Hi,

What is the purpose of the gear? Constant carry when hiking / camping? EDC? Gear for use when the grown-ups go missing? Make them carry regular stuff so you don't have to?
Anyway, here are some of my thoughts for additional gear:

• an id card of sorts with name, address, phone, parents names, etc. You could put the info on the back of the laminated family photo. For most grownups the equivalent would be a driver's license.
• a colorful bandana
• a plastic ziplock type bag
• let the girls personalize / decorate the waist pack some way to make it easy for them to identify their own, as long as their names are not clearly visible on the outside.

Thoughts for activities:

• swimming?
• storytelling / making up stories together
• singing songs
• plant / animal identification
• map reading (various types)
• intro to foods outside their normal cuisine (real foods, not eating bugs here)
• memory and observation building type games

Of course, my experience is with children younger that 5, so this stuff might be a bit simplistic for them.

-Kuovonne