I do charity stuff in my Vader, mainly around San Antonio. We've done things for Red Cross, SA Food Bank, and Special Olympics. When we do something, it's usually a 4hr event, and we normally raise about $150 each time. What really drives me is the kids. Some get scared, but most just love it.
If the 405th is going to do charity work, here are my opinions:
No exclusive charity.
We can do more good by helping many charities rather than just one. A main charity is good, but not an exclusive one. The problem with an exclusive charity is that there may not be local reps for everyone. That means many 405th can't do anything to help.
Charity isn't just fundraising
For the Special Olympics, we just hung out in Athlete's Village. The athletes and their families took pictures and got to de-stress from the competition. Visits to children's hospitals are especially rewarding.
Relax the rules
The 501st prides itself on having professional costumes. That's great for them, but in all honesty when that happens many potentially great members are excluded. And since our particular hobby here is especially custom-oriented, there is no real "correct" costume. Besides, you won't wear it if you're not proud of it. Also, the general public won't know the difference - I have a fair amount of detail in my Vader, but really as long as I show up with the helmet and cape, I'm Vader. No one says, "Nice quilted leather pants and great chestbox." Nope - it's always "I am your father" and "look it's DARTH VADER!" It won't change for Halo.
Be Local
I think the 501st has a good thing with the structure of their group. Since the 405th is very similar, a similar structure would do well - especially for charity events. The main thing being that there is one or two people who are devoted to setting up events. Events don't just happen, they have to be worked at.
It's dress-up
Don't take things too seriously. When it comes down to it, we're people who are playing dress up. When it becomes too serious, that's when people stop having fun. With the Star Wars group I'm with, we never take things too seriously, and if someone heckles us, that's their problem. We're having fun and helping out good causes.
Now, I'm no expert, but I've seen a lot and know what tends to work and not work. I think that many good things can come from the 405th if we really put the effort to it. And seeing how much effort has been going into the projects here, that shouldn't be a problem at all. Everyone here is really helpful, sharing, and giving from what I've seen. To me, that's the key ingredients to make everything work.