Hi Sparrow... sounds to me that your father isn't exactly as true believer! Which is good news.
Perhaps there's a better way of putting the problem to your father. There may not be a better organisation in his eyes, but there maybe 'other' organisations that would benefit more from his devotion, time and money. If he spent his time working for a charity, contributing to a charity and believing he could make a difference; surely more good would come from that?
Maybe if you took the lead you could involve him. Find a charity, humanist organisation, skills bank, etc.. etc.. and enjoy making a real difference in the world rather than 'waiting for an absent god'.
Whatever happens, good luck with it.