I think I also initially misunderstood your post- to be clear, you're saying the 10 items you list will be carried and the PSK is in addition to that? If so you have some decent options. If the $5 kit must cover those ten you won't be able to do much.

Provided the kids are already carrying map, compass, knife, matches, raingear, ett then perhaps a couple of contractor-grade garbage bags and mylar blanket would be good additions. A small fishing and/or sewing kit could be assembled pretty cheaply. Obviously, the items would have to be age appropriate.