Hi
Thought I'd answer your questions for a bit of help.
DDP is so easy. We have used it for years now. For breakfast just use a snack or if you are hungry the quick service breakfasts are quite big, big enough for 2 to share really. With table service meals, don't bother with starter as it's the main & dessert that are included but if you have starter you will have to pay for the starter & also will be too full for dessert (although you can takeaway most of the time). However there have been changes announced which I think means you can substitute the dessert for a soup or salad I believe.
We have done Disney with small children. It's fine, just make sure you take your pushchair, plenty of rest breaks & water. Have a few rest days too, just lounging round the pool etc. We usually do two days in parks, one day relaxing, two days in parks & so on.
We've stayed at Caribbean beach, Saratoga & Animal Kingdom. Personally Saratoga is my favourite. AK was lovely but I prefer the layout of Caribbean beach & Saratoga, with the rooms spread out around the property rather than a hotel as AK is. It's also very far away so journeys take longer & when we stayed there last year the buses weren't too good, not very regular. However after speaking to reception about it the service did improve. The restaurants are lovely & the food is amazing. It really is personal opinion & my OH's parents loved it, but I probably wouldn't stay there again. I hope this doesn't dampen your spirits at all as it really is just down to personal preference & I just prefer the layout & location of Saratoga.
Flights with toddler - well we were very lucky because our daughter fell asleep as soon as the plane took off when we flew with her at that age. However, it does get very uncomfortable having them on your lap for 9 hours, especially when they sleep because they get heavy like a dead weight! If there is an option to get an extra seat for them I would take it, but otherwise just try to swap between your lap, your husbands lap & little walks. I wouldn't walk them up & down the aisles too much though because of the trolleys & other people milling around.
Memory maker is great as the photos go straight to your band when you go on a ride & scan your band. Then they're all just there to view & purchase if you want to.
The weather is great in May. It's warm & the evenings are lovely. It's probably my favourite time of year because the weather is warm but bearable, perfect for children.
Meals & fast pass aren't stressful at all, especially with the new magic bands because you can pick 3 fast pass tickets in the morning before you even get to the park. So you can work out the timings around meals while you sit for breakfast & then your whole day is sorted.
Honestly I would say just go with the flow. Some days your plans will go without a hitch, other times you might find everything has to change because you can't get a table somewhere you wanted to eat or your little one might decide they're not liking your plans & just won't let you do what you want to do.
Have fun! We love it there & next year will be our 7th time : ) x