Talk to them about the percentage, not a good idea to just follow our suggestions to you how should be the dividend. Both parties should agree to the deal, win or loss. Since you are the one managing their money, try to include your "talent's fee" to them.

However, I don't know why these people offered you to trade their money. Do you mean they witnessed how good you are? Who are these? Friends or random people? I just hope they are really the ones who offer you to trade their money and not the other way around as I found it suspicious.