Hey Luke,
I've managed to get about 40-odd people to a social event/ride day at JAMS... pretty good attendance for a "fun day out" on the scooters... No pressure to be a good rider, just a casual day out with a few shots fired in anger...
Reckon if SAMBRA wants to entice new members, this is the sort of thing they need to put on... Non-competitive social ride days, not a full on race day...
Get a few riders in, give them a chance to have a swing at a proper MX track without the need for an MA license upfront, let them see for themselves where there skills are, and they can go from there...
Me personally, yeah i'd love to bring the minis down for a squirt around 3-Star, maybe even run the Blitz around there, see if enough work has been done to make it competitive around an mx track.. (probably not. ha ha ha)
Cost is the big thing though...
Get an approximate figure up front, and it will be far easier to gain interest...