i think base on amount wager and distribute base on it might be a better option.. 100 bets, people can simply bet 1 sat for each bet
Sure, it's the safest idea. But in case they have to play 100 bets they would have to stay on page and really wait for those bets to happen. Otherwise somebody could do 10 BTC bet and take all the profit on site (it's just an example).
Maybe set a min number of bets (eg. 100) together with a min number of bitcoin wagered (eg. 0.01 btc).
For anyone satisfying both the two requirements, they will get the same share.