i used to get them to make their own board game, write down the rules, then play each other's. that usually took up a day or two of camp, and required pretty much no prep or effort (and the kids loved it)

Clue is ridiculously expensive here.  Were you able to find an Enlgish version for less than like 40 or 50,000?

I found it on amazon for 8.99USD.
If you or a friend have "prime" you can send it to a secondary shipper like OHMYZIP for free. It usually costs about 8.00USD to forward.