We have eaten at both the Four Seasons and at Victoria's and Albert's at Disney's Grand Floridian. Both were very good experiences and the food was superb. We have not however stayed at either hotel, we have however stayed at other Four Seasons around the World and as you would expect the service was excellent.
You say you have found children so my advice would be to not spend full days in the parks as it is just too much for them. Our son is 3 now and we find it best if we get to the parks at opening and then leave after lunch. We then spend the afternoon playing by the pool, at the playground or shopping or whatever. A full day in the parks just is too much for little ones and I would say this is true up to the teenage years.
I would recommend a car because then you are not reliant on Disney buses and on taxis to get anywhere, even if you stay at Grand Floridan, Polynesian or Contemporary (the monorail hotels), you will still need to get a bus to Disney's Hollywood Studios or Animal Kingdom.
You say your kids are too young for Universal, are you sure? Our son loves Universal as he is a huge Curious George and Dr Seuss fan.
One other thing to consider is that if you stay on site at Disney is that you can make your fast pass reservations 60 days in advance, whereas it will be 30 days in advance if staying off site with tickets. Fast passes for the busy rides get booked up way in advance. I don't think the Extra Magic Hours for on site guests will be useful to you as getting into a theme park at 8am with little ones is almost impossible and you wouldn't want to be there late in the evenings either.
I hope that all helps.