My initial thought would be 8 players 25k sat buy in each for a total of 200k sats. 100k goes to the charity. Winner gets 100k or we can say top 3 split 100k maybe 50k to winner and two and three get their buy in back or something to that effect.

There is a lightning poker site. That would be ideal but we may need to use something that allows us to create a custom game.

Let me reach out to lnpoker and see if we can set something up.