Mike

That sounds excellent stuff.

You could try Parlauf and Triangle relays as extras.

Parlauf uses a loop split in half. In pairs one runner stands on opposite sides of the middle split. On go, the first runner runs round and tags the second. The first then crosses back to their starting point to wait for the second, who tags them... repeat until exhaustion or earlier. You can differentiate by not splitting in half, so there is a long and a short section.

Triangle relay has 4 in a team with three flags in a triangle. 2 at one flag, 1 each at the others. On go, one of the 2 runs to the next flag and tags and waits there, the tagged runner runs to flag three and tags. Repeat until all runners are back at their starting place. Hard to explain to start with, but fun when they get the hang of it.

Both can be varied with uphill/downhill, different lengths of legs etc.

Have fun.