We found our kids (then aged 4 and under) became really fussy eaters at Glastonbury. They’re normally good eaters, so i think perhaps just being really over stimulated, meant that they wanted pretty boring comfort food. We learned quickly to order one meal for us, let them try it, and then only order more if they liked it, as we were throwing away so much food before that. We also ended up relying on the same thing a couple of times; choc and banana crepes were always a hit, as was the roast chicken stall which sold heavenly potatoes, cooked in the chicken fat!
We tried to buy one meal a day, and then feed from our own supplies the rest of the time, but without going back to then van, so we needed portable and lightweight but filling food. We found small tins of baked beans, macaroni cheese, sweetcorn etc were relatively lightweight, could be eaten cold, were filling, and you just needed to pack a spoon. We took individually wrapped choc croissants/brioche and soreen/banana loaf. Dried fruits like apricots/raisins. Breadsticks/crackers and biscuits, biscuits and more biscuits. We also took a bag of those ‘natural’ jelly sweet snakes for each day. We called them “power snakes” and gave them to the kids/adults when they were lagging. The combination of the magic of the name and sugar always worked for the kids as a good pick-me-up. Pack way more snacks than you think you’ll need, as the adults will tear in to them too.
Then be prepared to sell your soul if the kids like ice creams. I cant remember what we paid at West Holts last year, but I swear it was over a fiver per lolly. And of course the kids want those at least twice a day!!