Scavenger hunt

[Palustris]

Ok, as some folks may know I have been known to write children's stories. I am in the middle of one now and I am stuck. It is set in the mid 1950's and is one of a series about a gang of 10 year old lads and their adventures (a sort of lower class William thing). So, the lads are visiting an old disused quarry now turned into a public park. I needed something to send them off exploring so I thought of a Scavenger Hunt. Trouble is I cannot come up with enough items for them to find. I have feather, gorse flower, daisy, acorn, sycamore key, piece of sandstone, small white pebble, bit of bracken, piece of other fern, match stick and clover. 3 or 4 more needed.
No damage to property or wildlife allowed, so no live creatures or their homes.
anyone got any ideas, pretty please? 

[Palustris]

[Jayb]

Blackberry, bilberries/winberries,  Hazelnut?

[Palustris]

Should have said, takes place in mid August and the things have to be put in a paper bag.
Thanks Jayb. Hazelnut is a possibility.

[Nora42]

horse chestnuts (maybe too early), cob nuts, damsons or sloes rosehips , crab apples.
not sure if that would help
Nora

[sparrow]

a sloe, a thistle head, crab apple, rosehip/haw, rabbit/deer dropping (you'd be amazed/revolted at what we picked up as kids! Cowpat frisbee anyone?) or tufts of bunny fluff from near the burrow, bottlecap.

Any of those any good?

[ACE]

Mid fifties. Silver paper. discarded in every cigarette packet.

[Palustris]

Thanks folks that gives me enough to be carrying on with the story.
Only been stuck on it for 30 years!