Will you quit the gambling for that month and give the allocated money to the poor family or will you prefer to gamble as you can't live without gambling ?
50:50, that's fair without disturbing one of them.
Instead of giving them 100% of the total budget then I prefer to give them 50% without interfering with my needs. Value is not what they expect, but our helping hand is what they want for any amount. Regardless of whether the budget is for gambling or not, then I think 50:50 is a fair percentage for needs and charities.