Everyday Paleo always has great school lunch ideas. Two favorite ideas I got from there include:
cucumber sandwiches: put shredded meat (I also eat Applegate Farms deli meats) in between cucumber slices and serve with guacamole or goat cheese
pure wrap: paleo wraps that you can stuff with any fillings (leftover meats, salsa, almond butter etc). You can buy pure wraps online at:
Improv'eat ® Beyond Organic. Beyond Compare.
Those ideas can act as the "sandwich" for a school lunch. Maybe add some cut up veggies, cherry tomatoes or pieces of fruit. A larabar can also be a fun addition to a kid's lunch bag. If your kids like pickles, real fermented varieties can be a fun snacky side item.
Hope that helps!