I think it really depends on what budget you have. There's no point saying "Yes, the DLH is great" if you have a budget that won't stretch that far IYKWIM? We went over a weekend for our first trip, stayed onsite at the cheapest hotel (Santa Fe) just to see if we liked DLRP and the whole staying onsite thing. We loved it and we are going back next year, but for 5 days instead of 2 and staying at a slightly better hotel. I guess it also depends how long you want to spend at each place, you'll realistically need at least 2 days at the parks, so if you want to do a couple of days in Paris too then you need to look at a 4/5 day trip as a minimum. If you only want a day trip to Paris, then stay onsite and get the RER into Paris for a day, if you only want to do the parks for a couple of days and mainly visit Paris, then stay in Paris and travel out to DLRP.
My must sees for Paris with littlies are the Arc De Triomphe (sp?) and the Eiffel Tower. Perhaps Notre Dame and the Sacre Cour and a boat on the Seine, look round the Louvre. I reckon you could "do" the major sights in a day unless you want to go really indepth, it depends how old the kids are I guess.
I guess my top plan would be a 4 night 5 day trip, 2 half days and 2 full days in the parks, and 1 full day doing the main sights of Paris by RER and metro. Stay at the DLRP hotel that best fits your budget and travel by Eurostar so no driving.
Does that help? Probably not LOL!