Old post but Geocaching is another great app that gets kids excited to go out adventuring. The more difficult finds can incorporate map skills and require hiking into difficult terrains. Both naturally need some types of prepping and it can be a “gateway” activity into lowkey prepping.
This was me 5 years ago and man how time flies! In all honesty I was prepped to shelter in place or car camp if SHTF. Each kiddo had their own child sleeping bag and a “BOB” (youth LL Bean backpack that they eventually used for K-2). Those items were used for camping trips that got the boys used to the mechanics of it all. I also had a heavy but very warm rectangular sleeping bag that could have been used for cosleeping, again with the idea that we are hunkering down at home or in the car.
I also had a great 3 wheel jogging stroller that did well “off roading” and could carry both kids and and a week of groceries (more if I wore the little one) so that could be an option as well if you are in a more urban or not super woody undergrowth area. Biggest thing with that would be practice to make sure you have the stamina.
Anyway…if you got the packs at a good deal hold onto them. The kids will be big enough before you know it and in the meantime they could be the BOB for the car or something. If no, return them but don’t know that I would invest in specialty items that would only get a few years use if any considering how kids grow. Like someone else said maybe swap for a quality full sized bag that the kids could share now and one day could be their actual bag then you’d only have to buy one more.