Containment: They're too big for a pack and play, and without a gated area, it takes two adults to wrangle them.
Bring a pressure gate - no guarantees there will be a place to use it though. Perhaps a tablet loaded with appropriate movies and games will slow them down a bit for a little while.
Food: No molars yet, so adult food choices are somewhat limited. What to pack for them? They,re not picky eaters, but at 900-1000 calories per day per kid I can't just feed them goldfish crackers and Nutrigrain bars.
For a day or so you could. Cheerios too. Trail mix. Applesauce in those little to-go packets.
Sleeping: Not willingly, and I don't want to leave them strapped into a stroller overnight.
Supervised napping -- in other words, bring them into bed with you, one per parent if you can. Otherwise you're most likely strapping them into the stroller overnight.