Never been to Disney, but have recently returned from a sun holiday as a size 20 with big boobs, and have previously been on holidays as a size 24.
I spent years in black linen trousers in summer, because I dislike my legs. I made a conscious decision not to buy any more as it’s so hard to get ones that don’t immediately look crumpled and go baggy after wearing for a few hours. Instead, I have some thin, loose cotton trousers that hold their shape better and are cooler than black linen.
Light dresses with snag chub rub shorts are great, I add a belt to most dresses otherwise they just hang off my boobs. Use a hair elastic as an additional belt loop if necessary. I’ve had surprising success with midi dresses from Primark (via Vinted for me but presumably also in store), 100% cotton, not lined but not see-through either.
I wore shorts this holiday for the first time since I was a kid, and felt less self conscious than I thought I would (and usually do in summer clothes generally) and realised it was because I was dressed suitably for the weather, like everyone else, rather than trying to hide my legs. Having said that, I make sure my shorts are almost to my knees, and have some structure to them, as I don’t feel comfortable with thigh on show.
Sainsbury’s is good for sleeveless tops that don’t cling to every bump, either wide-strapped sleeveless tops or sleeveless shirts. I don’t like my arms but the difference in temperature was surprising, and I’ve continued wearing the tops since being home, when it’s been warm enough.
And obviously, your most comfortable shoes!
Have an amazing holiday!