Cali,
The dogs will love it.
A few things. They really have to be well trained. No compromise here. I kept Vrka on-leash on a local rail-trail. She'd heel or run ahead (actually pull me) as conditions dictated. The cues were "Heel" and "OK" for, well, "Heel" and "go ahead and run." She really enjoyed pulling me. Bet yours would, too. They were bred for it, after all.
I used a harness instead of a collar so I wouldn't choke her. Just the regular one one gets at the pet store, as I recall. She would come running when I got the leash and harness out. Didn't even have to call her.
On MTB trails the dog MUST come when you call. And stay away from your wheels. I don't think I'd try that on-leash.
As I said, Vrka and I had a blast, but I've never had another dog I'd do it with.
Give big space to the festive dog that make sport in the roadway. Avoid entanglement with your wheel spoke.
(Sign in Japan)
1978 Raleigh Gran Prix
2003 EZ Sport AX