I don't have kids myself, but I have many nieces and nephews, and my siblings are always asking me to take them out hiking with me!
So, I'm finally giving in. However, I don't know what to have them pack in their bags! I've been doing some research, and it seems that I really need to just give them the very basics, and be prepared to carry their packs on the way back if necessary. Not a huge problem, but good to know!
Note here: this post is directed to those that are toddlers and preschoolers! Older kids can scale more and more in their packs and you can find more of those guides on line, but this is one of the only ones I could find directed at toddlers and preschoolers! It may be a total hassle to take them out at this age (I'm guessing they will want to stop and touch everything) but the earlier you expose them to the wonderful world out there, the more they might love it!
For a Toddler or Preschooler, consider including the following (make sure to consider how big they are for their age as well!! This is an important factor):
Junior sized pack
Rain jacket (full rain proof)
2 pairs gloves (or, 1 mittens and 1 gloves)
Sandals for warmer months
Sit pad (Thermarest)
Whistle (Connected to front of pack, for easy access, taught only for emergencies!!)
Insulating layer (jacket, fleece)
Garbage bag (quart freezer bag)
Extra pair socks, pants and underwear
Water bottles or juice boxes