1

You need to check with the hire car provider for the Eastern European countries such as Czech Republic, Slovakia, Hungary, Croatia, Serbia and Romania. Rules vary by provider. The only way to be sure is to check their websites or phone them up. Major providers over here include europcar, hertz, sixt and Avis. Penalties will apply for one way hires and/or de-hiring in a different country, but these are shown up on the website before you click the reservation button to confirm.

However, what concerns me is that you intend to do all that lot in 20 days. Given the other members of the party are older, they may struggle with a punishing routine. My suggestion would be to deep dive into 4 or 5 places only. Also, given there's 5 in total, if you do hire a car, get a minibus, cos a big saloon's gonna struggle to accommodate 5 people + a suitcase for all.

I suggest you also hit http://www.viamichelin.com to figure out your itinerary, likely fuel burn (fuel prices are very high in Europe), duration and any additional costs (e.g. motorway vignettes in France).

As an alternative, it may be easier all round to use the trains, cos they may even be faster and less effort overall (parking in many major European cities (especially the Italian ones) is a major headache. For example in Germany, specialised group tickets are available for regional travel - 5 people can have an all day ticket for 68 Euros.

Finally, yes, June-July is high season.

2

If you must drive, think about leasing a car and start from France. The French have a special lease for non-EU citizens (not sure where your are from) that works out cheaper than hiring a car + insurance. You own the car for the 20 days plus you are comprehensively covered in case of accidents, break downs etc and when you return in (in France, if you can manage this, will save you massive extra fee for out of the country drop-off) the car manufacturer buys the car back off you (you just sign the paperwork, no money changes hand at the time of the buy back).

You chose from Peugeot or Renault. Talk to a car rental broker in your country. For Australia I used these guys http://www.driveaway.com.au/ They are very professional and I have used them for rental in other countries as well.

You can drive pretty much any where in west, central and esatern Europe with a few exceptions - notably Serbia, Bosnia and Herzegovina back in 2008. This may have changed since so check the T&Cs.

Also I'm with Fwoggie too many places for 20 days, The rule of 3's works out about 5-6 places max in 20 days.

3

In case you're from the US these people have good recommodations http://www.gemut.com/, even if you're not there is a lot of info about car rental, one way fees and so on in this link.

Like others said before you're trying to do to much, 20 days and 10 countries will give you 2 days per country, actually not even that if you deduct travel time, choose a smaller area.

4

11 countries in 12 days? That's a day and half per country. Subtract driving times and you have a few hours to sightsee in each country. Good luck.

I hope you realise that this is a nonsensical question. I know a great hotel in Kosice. And outside Bordeaux. Why should i make the effort to write this down if I'm not even sure if you're going to come close?

Figure out what places (not countries!) you;re going to and then you can come back with hotel questions. With a budget in € please.

and read this:
http://www.lonelyplanet.com/thorntree/thread.jspa?threadID=2153476