Hellobee Boards

One thing DD likes to do is tie sticky tape around her wrist then go on a walk and stick flowers, leaves, berries etc on it to make a nature bracelet. Make paint out of soil, leaves etc by crushing it with water. Make faces on the floor or sand with things from nature......
I don't really know what to suggest your older kids.... Rounders is a great game for all ages if you have one bat and ball though.

I'm a sucker for fun competitions. Things like:

- build your own mini leaf/twig boat and either race them or have them carry things ... whichever boat stays afloat longest wins
- teach them some simple crafts like bracelet making and have a special secret bracelet exchange (all it requires is string)
- look-up facts about specific plants, rocks, seashells and do an informative lesson highlighting an interesting story about one of them
- DIY kinetic sand (sand, corn starch, dish soap, and food coloring) session
- sand castle competition
- make cards for their parents - something to take home and share
- construct a huge magical fairy house to be put on display ... the big kids can do all the major construction, smaller kids can gather materials, dried flowers ... the more rustic the better
- if a big fairy house is too ambitious, how about a fairy village ... just requires a few pieces at a time

I think a scavenger hunt could be fun with those ages.

Minute to win it type games

My DD is a little younger, but she loves doing obstacle courses. You might have to be a little creative about what to do, but you could lay out sticks for them to hop over, use rocks like cones for them to zigzag around, set up a tunnel to crawl through with some rope and a blanket or tarp, make a balance beam from a log (if you can find one that would be safe enough), etc.