As someone else said, I'd share at RFC on the AK day. The food isn't amazing or anything, but it is good and their portions are plenty big enough for sharing. At the one up here, my mom, DD8 & I have shared one appetizer and one dessert between the 3 of us and left feeling full!
When it comes to snacks at AK, I really don't feel like there are any must-dos, so I'd probably pack some granola bars, fruit, goldfish crackers, and things like that to snack on during the day. That way, the only snack you might want to buy is a frozen lemonade or other cool treat in the heat of the afternoon.
At MK, it would really depend on how long a day you're planning. We usually have breakfast before our day there and dinner after we leave the park for the evening, but we go during slower seasons when the park hours are fairly short. What we do in the park is share the must-have snacks; a turkey leg, a Dole Whip, a cookie ice cream sandwich. We share so that we can all try a few bites of each, rather than filling up on one and missing the rest!
As far as meals to share, Cosmic Rays chicken & ribs combo is probably the most shareable counter service meal anywhere at Disney - a half chicken and half slab of ribs with potatoes & veggies for something like $15.