If you are talking about shows, they usually allow 1-2 companions to sit next to the wheelchair -- others may be in a row or two ahead or elsewhere. If they allowed your whole family to take up all the companion seats, that would mean other guests would need to sit completely by themselves without anybody else from their traveling party. The wheelchair seating is often cut-outs along the back row, with space for a wheelchair, bench for 2 companions, space for 1-2 wheelchairs, bench for 2 companions, etc. If your family is mostly very young children, I'd suggest you plan ahead taking turns who sits with whom.
For ride vehicles, they are limited to the seating designed for that ride vehicle -- some seat 4 and some 6 or 8. A few of the boats may seat 10. Again, depending on whether anyone is young enough for a lap or baby carrier (generally under a year old), you may be able to fit. But I'd expect to be split. There is information about ride vehicles in the disABILITIES FAQs thread pinned near the top of this forum.
Enjoy your vacation!