I was recently thinking about the same thing. I recommend starting small and giving to every cause you like, including causes that don't have 501c3s. Start with a small amount, maybe $1k or so, and the same amount for everyone. They'll all want to treat it as annual, so don't overdo. Then once you know them better, decide whether you're happy with it, want to increase it, or want to cut it before they ask for an annual contribution.

I also pick one month of the year for all of it so you don't make 3 "annual" contributions a year. My parents used May, for tax simplicity I think, whereas I use December so it can crowd out with giving to people I know.

This is assuming you're looking to give primarily. If its largely a tax question ask an accountant. Just remember, "they can only bury you with one set of golf clubs." Once you have more than you or your family will ever spend on yourselves, better for you to dispose of it than your heirs.