Hi gusfus,
Firstly, if one has to be insane to visit DLP in July or August, then I must be well overdue for the men in white coats to carry me off, as I have been going there in summer holidays since it opened as EuroDisney with just the one park.
There are only a few rides there which have height requirements - most rides are suitable for children over 1 yr, and some are also fine to take babies on.
It is very difficult for other people to say which rides your children will enjoy the most, as so much depends on the individual - some kids are braver than others. My 3 yr old nephew thought Fantasyland was too babyish, and wanted to go on Big Thunder Mountain, Phantom Manor, and Pirates of the Caribbean rides all the time! He was very upset that he could not go on the roller coasters like his older brothers. If Tower of Terror had been built then, he would have gone on that as well....
Some young children are more easily scared, and prefer calmer rides, so it is very much a case of knowing your own family. My eldest son loved BTM when he was young, but my younger one was not keen until he was about 7.
The Snow White ride in Fantasyland can be scary for some as it features the Wicked Queen and dark forest.
There are plenty of rides, attractions, shows and parades for all the family in both parks. Adults can go on everything apart from the two kids play areas in the Disneyland Park, as these have maximum height restrictions, and only for small children. One parent can take a young child to play here for a while, and the other can take an older child on some rides. Our boys have a 4 1/2 yr age difference, so we used to spend some time together going on rides, and some separately so each child could choose what they wanted to do.
Disney do something called Babyswitch - this means that parents with a younger child or children who are too small to ride can take it in turns to ride whilst the other stays with them. An older child can go with each parent, so can have two rides. Just ask the Cast Member ( staff ) at the ride entrance, and they will explain what to do. We can also explain on the Trip Advisor Disneyland Paris / Marne La Vallee forum, as well as any other help you need with planning your trip.
www.tripadvisor.co.uk/ShowForum-g226865-i2224-Marne_la_Vallee_Seine_et_Marne_Ile_de_France.html