Chicago to New York

Chicago to New York City (?) is a 12 hour drive plus stops plus Chicago IL traffic plus Gary IN traffic Cleveland OH traffic plus New York City NY traffic by the shortest route. The only attraction that is along the way would be Cedar Point, the center of the roller coaster universe. Places like Kelly's Island, the Henry Ford Museum, Sleeping Bear Dunes, The Gettysburg Battlefield are farther out of your way and each is an all day stop by itself. Cedar Point would be an all day stop too. I-80 across Pennsylvania is a scenic drive.
How far do you want to drive in a day?

There's more to the Cleveland area than Cedar Point.
Depending on your taste in music, especially kids of that age, there's
https://www.rockhall.com/
the R&R Hall of Fame.
Let's hope the National Parks will be back open again long before your trip. A nature detour in the Cleveland area would be the Cuyahoga National Park.
https://www.nps.gov/cuva/index.htm
If you want to go on to Niagara Falls, head east from Cleveland on Rt. 90 to Buffalo.
From Buffalo to NYC, how much time do you have?
You can continue east on 90 and cut south from Rochester through the very scenic Finger Lakes, then southeast from Binghamton to NYC.
If you belong to the British auto club, whatever it's called, you are probably eligible for AAA services in the USA. In any case, you need to get good hard-copy maps for planning. The possibilities are endless. The AAA also has state guides, etc. Check online what info/printed matter you might be able to obtain from abroad.

Besides a "nature break," what do you consider interesting? History? Art? Music? Food? Hikes? Bikes? Night clubs? Strip clubs? Remember, we don't know you and what we like may be what you hate.

With five people, you may find it cheaper overall to rent the car.

If you want a "nature break", go on I-80 through Pennsylvania (Keystone Shortway). There's plenty of places to stop off for a break. Buffalo is highly overrated unless you explicitly want to go to Niagara Falls, which is not even in Buffalo.

Also a buddy of mine used to drive for Trailways of New York; you can get a coach ride to the Finger Lakes or anywhere else in New York: www.trailwaysny.com. Only qualm is that some of their H3-45s have uncomfortable Premier LS seating, which we all hate. Their owner Eugene Berardi switched to other seats in later orders, though the older units still have the most comfortable National 4210A seats. (I'm a motorcoach geek!)

Your profile says England, so for the car option, I'd go online pay the $7 Canadian each to attach an Electronic Travel Authorisation (ETA) for Canada to your passports beforehand, and then do a night in metro Detroit (it's got some interesting parks like Belle Isle, museums, etc.) cross the border into Canada, and then a night in the Toronto or Hamilton area before visiting the Falls from the Canada side and then crossing back into New York state from there.

Do verify you can take a rental car into Canada beforehand, but the big name rental companies generally have no problems with that.

AAA (or British reciprocal membership) is often good for about a 10% discount at a good number of hotels and attractions where you can 'show your card'.

Niagara has park land along it, but I wouldn’t describe it as a nature break. I don’t think Detroit would be all that interesting as a stopover and southern Ontario is pretty forgettable. Cedar Point would make for a nice way to break up the trip—-there’s a beach as well as amusement park. I would suggest Canada for better views of the falls, though.

The traffic going S from Chicago is not as bad as other directions and if you take the Skyway toll road, you’ll miss the worst of NW Indiana traffic is mostly a function of construction and often poor road conditions on. I-80 in the Gary-Hammond area. Cleveland traffic is not bad, except during rush hour. Cleveland could make sense for an overnight with some planing. The Blossom Music Center is an outdoor music venue—-popular music and light symphony program. You can sit outside and oinic. The art museum is open 1-2 nights/week. The armor exhibit is a perennial favorite among kids and it has a nice park setting. Cleveland also has a nice park system and if you stayed in the East Side, Squires Castile would be a nice evening destination that has a picnic ground.

Buffalo has no visibility as a tourist destination but has good art museum and some interesting neighborhoods and it lacks the tourist trap atmosphere of the Naiagara towns. It might make sense as an overnight if you planned a full day at the falls.

An alternative route would be via Indianapolis and Columbus to DC which are among the dullest cities imaginable and then through low mountains in Pennsylvania, but you could cut down from Columbus through a series of National forests in Ohio. And West Virginia which get more interesting in West Virginia. Seneca Rocks would be a nice nature break on that route. Athens, Ohio, a university town with a quaint center would b e a good overnight. You then pick up I-66 in Virginia on Us 48 to DC.

I-80 is pleasant but not the kind of nature break you probably want.

If you're going through the mountains of Pennsylvania, you might as well go I-80 or US 6 (or US 22 or 30) instead of the Turnpike. Any of those could be scenic if you pull off at the right places. If you go US 30 you can stop off at Philadelphia. Obviously none of this applies if you're going to Niagara Falls.

Hi, thank you for your input. It is really helpful. If we were to drive, we would go around Lake Michigan towards Grand Rapids then cross East to Sarnia where we would stop over for the night. That's 5h30 drive so a full day driving with breaks. Niagara falls are 3h drive away which could be done the next day. The only way we would do this is if the route was really scenic which according to your comments it doesn't seem particularly to be. We would go along Lake Michigan and Lake Huron for a bit but it would mostly be crossing Michigan (which does seem exciting from here in the UK but might not super interesting after a few hours in the car. Correct me if I'm wrong!).
At the moment, I am more tempted to take the Lake Shore night train between Chicago and Buffalo, then spend 2 days at the falls (we saw you could cycle on the US side in the State park). Is it even possible to sleep on Coach seat?
Afterwards I saw the Maple Leaf train from Niagara falls to New York followed a scenic route amongst the Finger Lakes. It has the advantage of leaving from Niagara falls so we would not have to return to Buffalo. We could stop at Rochester or Syracuse then hire a car for 2 days and explore the lakes (go to Watkins Glen), then take the train again for the second leg to New York. Has anyone done anything of the sort? Does it seem doable?
The other option is to hire a car from Niagara Falls or Buffalo to New York: the falls to Watkins Glen is about 3h drive then a further 5h to New York. This could be done over 3 days.
I have to say the train option seems less tiring but we need to decide if it would be flexible enough.

Thank you for the link to the coach routes. It might be useful to get around the Finger Lakes from Rochester or Syracuse.