I was suggesting the other direction to avoid Mtn. bike traffic as much as possible. I don't see any reason why shuttles from either place would be any different, unless you're hiring some commercial shuttle who only knows how to get to Kenosha pass. Plenty of parking at both places.
When you say "weekend" not sure if you're talking Friday-sat-sunday or just Sat-sunday... if the former, you should be fine with bikes in section 3 (where you're starting, right?), but section 3 on a Saturday would be heavy with bikes. If you started at Kenosha and hit section 3 late on Sunday, shouldn't be as bad.