I will add a little to the OP's topic on how to improve quad turnout. I am fully aware that quad turnout has declined over the years. Also, the number of riders looking to just practice have decreased to the dedicated local riders and the National guys. There are not a lot of riders that go to practice during the week that aren't really into racing local or Nationals. Years ago, in the hay days-2004ish, you can find 10-15 guys that were the average rider, 10-15 of the local racers and 5-10 of the "National Boys." This past year I know a lot of my friends (close to 12 that ride) did not have the money or time to ride. Business picked up and they had to work, 1 broke his back, another bought a house, throw in a bunch of new additions to the family and my local group is dwindling.
Quad Practice has to be moved to either Monday, Tuesday, or maybe even Wednesday. I will give you first hand advice from racing Nationals since 2003. I have been to A LOT and raced a lot as well. Many of the National guys are packed and loaded on Wednesday and leave for the track on Thursdays. Of course, they aren't going to practice on a Thursday. They have a regiment that follows the racing schedule. If you want to entice Upperman, Hammie, and any of the other National guys, you cannot expect anyone to come on a Thursday. I have never went to a track on a Thursday during the Nationals. I've done only a few Wednedsay practices but that was 2004-2005. Why didn't anyone show up the weeks after Nationals...? I surely don't want to continue to practice or ride after 30 weeks of a non-stop regiment of training/riding/racing, etc. We/they need a break and the weeks following the season is that time period.
If Tuesday is normally a dedicated bike night, then state, "Hey everyone, we are giving this a shot. We want quad riders to enjoy our track too so the whole motocross community can enjoy what we have established: a highly recognized track. Quad practice will be on Tuesdays, but we are not excluding bikes. Just understand we are catering to them (quads) on Tuesday and it is their day on the track. Feel free to come ride." Consider it an open practice but let it be known that day is for quads and if there are any complaints from a bike rider to 'deal with it' because you have to entice to quads." I don't see why an open practice is now possible or both to enjoy. OIR had days of combined practices, but that didn't happen for too long. To the quad riders' dismay.
A phone call away - Mark, Jodi, Laz, & Tom (Baldwin, JB, GT Thunder, & Atv Fourplay, respectively) are very well connected in the atv community. A simple mass email to them to help promote your track for them to put on Facebook. I can see most of the local shops willing to support (via free mass media) our local tracks. Don't forget ProQuad, Six5, HMF, Wiseco, Cometic, and many other establish firms in Ohio. Ohio Crew is a good resource too. They are actively involved into Ohio based racers. Ohio has a very large group of Motocross guys, but you have to (and many tracks have) keep pushing into newer advertising territories via the local shops. Maybe call or make some flyers for the local Honda or Yamaha shop. If that flyer turns in 1 sale... BOOM paid for their efforts. Baldwin does bike engines too. Why not try to contact him for some cross promotional work? I'm willing to venture a guess he may be interested in entertaining a discussion about this all.
I'm no one special, but I always try to look at things from a fair/equal perspective. WE ALL WANT TO RIDE/RACE. I have no problems practicing on a track next to a bike. He/she wants to ride as do I. I respect them as they should me. Share the track. Rip your motos. Let's all have fun.