One suggestion I have for anybody going to WDw - no matter your size -is to think about all the walking. It's ALL day at WDW. If you are able to go for walks each day, I strongly advise it. Even if you plan on getting
scooter for help, the more you can get in shape before you go the more fun you'll have. If you can go for 30 - 60 minutes walks every day before your go ofr at least a month, you'll really appreciate it at WDW. plus you'll lose more weight!
Make certain everyone has the great walking shoes. Don't skimp! Break them in, but get something really meant for running or walking (I prefer great running shoes) - and I prefer to have at least one pair of high quality sandals and one pair of sneakers to trade off. A good pair of shoes will double your endurance - seriously! no matter how good a pair of shoes, you will need to be able to trade them off with another pair. A third pair of pool type shoes can be good for water rides and the pool. (OR if your sandals are okay with getting wet. Never wear sneakers on Kali!)
Have a great trip!