I have to say, I've been meaning to come up and race for months, but sunday is the only day the wife and I get off together, so the daytime race times were a problem for me. However, I've just noticed the evening race times, and it certainly makes it more appealing for me, at least I still get a full sunday.
How about switching each week, 1 week evening and one week days. It might get confusing, but it does give those people who can't attend during the day a chance to attend, and it also give those that can't race on the evening a chance to attend too.
Alternatively, sunday, 7-10am
As for people not putting the track away. Increase the cost to race a couple of quid, those that help out get racing at the current price. That way, those who don't want to help have the option of paying more and not helping, those who want to help feel like they're getting something for it. There's got to be some kind of benefit for people to help, sadly, that's how things work these days. Once you've helped out for 4 week, you get a free week?