Without knowing specifically which limitations your children have it's difficult to offer personalized suggestions. What I can tell you though is that most of Disney's attractions are accessible to all guests, including those in wheelchairs. There are also special parade and show viewing areas reserved for guests with limited abilities. For more information, take a look at the
Guests with Disabilities FAQ. Of course, you are always welcome to stop in at Guest Services as you enter the park and talk with the cast members there about any questions or concerns you may have. I've always found them to be very helpful in directing us and offering suggestions.
If your children have special dietary needs to consider, be assured that the chefs in the restaurants attempt to accommodate various dietary concerns. Call Disney dining at 407-WDW-DINE for further information.
You may also consider attending a character meal or two. If you do, your kids will have an opportunity to meet and greet various characters without waiting in long lines; the characters will come right to your table.
I have a daughter with special needs who absolutely loves our trips to WDW. With a little planning your children are sure to have a magical time as well!