Thanks for the suggestions.
I like the weekly contest idea - I have been looking at a few different ways of running it. Just waiting for our membership to grow a little more before I start it.
We reinvest all the rewards (directly or indirectly) in increasing the Steempower so as to maximize the value of the upvotes for each member. Even with the low value of Steem as it is now, a daily vote of $0.12 for each member adds up to $3.60 worth of upvotes over the month.