What my grandkids need to be comfortable is a good hipbelt (remember that little kids don't have much hips) and load lifters to keep the pack weight from pulling on the tops of the shoulders. My older grandson is especially sensitive to shoulder pressure--more so than his younger sister. I can sympathize because I have the same problem!

My own experiences with external frame packs were unhappy enough that I'd rather not inflict one on the kids. When I was using an external frame pack, it seemed to have a life of its own, zigging when I zagged, and I had several falls as a result. The internal frame pack moves with me instead of against me.

For kids younger than 7, a day pack with hipbelt is fine, since they shouldn't be carrying much weight (maybe 4-5 lbs. total)--just their wraps and rain gear, water bottle and a snack is usually enough. Unfortunately, such a pack for little kids is hard to find. Granite Gear used to put out a little kid's daypack called the Sidekick, which had a nice stiff foam back plus a hipbelt. Unfortunately they discontinued it a couple of years ago. I was able to get one on closeout, and it's waiting for "Bear" (who just turned 5 this week) to go on his first backpack trip next summer!

LL Bean makes packs for preschool/kindergarten age kids. If you're a sewer (I'm not), you could add a hip belt to help the shoulder issue.

For school-age kids old enough to carry 7-10 lbs., if you can find a used kids' backpack with the support system (stays, shoulder straps, load lifters, hipbelt) in good shape, just cut off the bomber nylon pack bag with its zillion gewgaws and sew a simple bag out of Dyneema to replace it. With smaller children very limited in the amount of weight they can carry, I hate to have half the allowable weight be the pack itself! For one thing, I have to carry the difference!

Unfortunately, I'm not a sewer, so that solution isn't feasible for me. I wish it were!

I'm glad you're already taking your grandkids out! It's so much fun to watch them discover the outdoors!