On the side of my poker table building business, I also offer rentals for charities and fundraisers. You have to think about the type of people you're going to be inviting to your event as well as what type of event you want to host.
Scenario 1. Poker tournament fundraiser. Your invites will be poker players who want to play in a large tournament. Rake is normally 50% which almost everyone is fine with knowing it's a fundraiser. The event should revolve around the tournament. You should have rebuys and add ons as a way to generate more funds as well as sell drinks and food, pizza is ideal as it's easy to sell by the slice. 50/50 tickets are a good idea too.
Scenario 2. Party with poker. Your invites will be anyone who wants to come to a fundraising event to party. There would be music, dancing, mingling, and side activities. Of course poker would be one of them, but you could also have blackjack and a prize wheel and other money making games. You can let people buy play money and move around the event during the night playing the games to accumulate more play money which they can cash in at the end of the night for prizes or raffle tickets. From the money you collect, you would retain a percentage to go towards the fundraiser. Of course you sell drinks and food again to raise more money. In this event, you could also do mini tournaments for poker and/or blackjack. 30 minute rounds where whoever has the most chips at the end wins.
In my experience, #2 usually has a much higher attendance rate than #1 but #1 generates much more money than #2. If you can manage to get a decent turnout of around 50 players with a buy in of $50 each, you're looking at $1250 towards the fundraiser right off the bat. On top of that, you can count on more money from rebuys, add ons as well as the drinks and food and 50/50 tickets.
In #2, though you will probably get a better turnout as you're not excluding any non-poker players, people don't usually spend as much money on the gambling. Cash buy ins are usually much smaller and anyone who isn't familiar with the game is usually reluctant to sit down with those who know the game. This is strange to me since I often see people buy in for $40-$150 in a tournament when almost zero poker knowledge to help support the fundraiser but would never do the same if it were a cash game.