I have kids who have gone through Kohanga Reo, primary school, intermediate and high school and I tell you the #1 rule for fundraising is this:
Attract punters from outside your community
To this end, I reckon a kids-oriented, light & fluffy, everybody wins, linear style simple fantasy battle adventure is a good idea. You select a good park/free location in which you offer a 1 hour + adventure for small groups (6-8) and then you set up a series of encounters for the kids to enjoy. Market it to local schools (within say a 10 minute drive of the location).
Book groups into 15 minute slots, give each group a couple of guides to make sure they follow the linear path and you're done. Parents can either follow along to take photos and watch, or else drop them off, have a coffee at the local cafe and then pick the kids up afterwards.
I've run lots of these (e.g. as fundraisers for the Green Party), as long as the rules are simple e.g. the following types of character class:
fighter - can use shield
mage - can use magik (spell packets, buffs etc)
healer - non-combat and can heal
rogue - can us a sneak ability for subterfuge encounters
then the kids pick it up with minimal training required.
I reckon you could charge $15/kid of this - they get an adventure they've never had before and will rave to their parents for days about it. So you could get $1000 for processing 10 groups in the space of around 4 hours plus setup/packdown. It does take a good marketing and communications strategy, but it's a fundraiser makes good money and everyone has fun (it is a lot of fun to battle kids )