How many player were you thinking of making each table?
If only 8 then I think 15 minute blinds are fast but ok acceptable. We play with 15 minute blinds all the time at our game, though we usually have only 5-6 players.
I agree that 1500 in chips isn't probably enough, i'd go 2500.
blinds
25/50
50/100
100/200
200/400
300/600
400/800
500/1000 tournament's probably over by now or very soon.
Some will be over in an hour, some won't. Sure it's not really geared for skillful poker, but it's fun and raises some extra $ for the charity.
I agree that if you do this then you need to have dedicated dealers.
btw, I hope you're using Faux Clays for this event

.
Mike