Hi there. We took our 3yo a few years ago and it was great. Actually Bali is one of those places that is even better with kids than without as everyone seems to make an extra fuss of children there. Re the food, I think you would be pretty safe with things like rice and anything else cooked and/or more plain food in a big hotel. I remember we took a few bits and pieces along with us in case we couldn't always find suitable food for our daughter, eg, cans of tuna to have with rice etc but I don't think we ended up needing it. No harm in taking it though as it doesn't take up much space in your bag and you can use that space for something else when you are travelling home.
One thing to consider with a young child is the lack of child car restraints and/or suitable fittings for them in cars/taxis. Also pools aren't generally fenced so you need to take a bit more care with things like that than you would at home (depending where home is). Another thing to think about is how to transport your son when walking around, ie, footpaths not all that stroller friendly but 18mo might be a bit big for one of those backpack carrier things. We ended up making our 3yo walk a fair bit which I think the Balinese thought was a bit mean (kept having people offer to carry her for us). Also took a cheap umbrella stroller with us for use in places like airports and shopping centres (was good as it could fit into overhead lockers on the plane which was great when landed really late at night.
In terms of places to stay, my recommendations are probably a bit old and may not be consistent with your budget but we stayed at Udayana Eco Lodge up in the hills behind Jimbaran Bay and Kubu Bali at Candidasa and both were great (although you need to be prepared to hike up a lot of stairs at Kubu Bali). We also stayed somewhere in Ubud which I probably wouldn't recommend as it was right on Jalan Monkey Forest which is really busy these days. Would probably go for a quieter village around there if going again. (Ubudian who posts on the SE Asia branch here can probably recommend somewhere really good).
All the best.
ENG
Edited by: empressnasigoreng