Hello Laura! What a lot of fun you and your sister will have bringing your kids to Walt Disney World for their 1st visit! Be sure to pick up complimentary 1st Visit buttons that the kids can wear throughout their stay - they just may get a little extra attention from the Cast Members! You can get them when you check in at your Walt Disney World Resort, or at Guest Relations at any of the theme parks.
Most moderate rooms sleep 4, in 2 queen beds. Including you and your sister, I'm counting 9 people, although your 2 year old could stay in a standard moderate room in a pack-and-play or tucked in a bed with 2 other little people for no additional charge. However, if you stay at
Disney's Port Orleans Riverside in the Alligator Bayou section, you will have room for 5 with 2 queen beds and a pull down murphy bed. You could request connecting rooms, which would have a door between the two rooms, or adjoining rooms, which will be beside each other but not have a connecting door. Requests are not guaranteed, but they do their best to fulfill them. My family loves Port Orleans Riverside, and it is our favourite of the moderate resorts at Walt Disney World. They have a great themed pool and lots of fun activities, as well as boat transportation to Downtown Disney. They also have a great food court, with lots of kid-friendly options.
Please let me know if you have any other questions. I would love to help you out, but I'm limited by space , so just write me back if you do. Have a magical day and have fun planning such a great milestone in your children's lives!
Kristen