I would suggest skipping the park. The trails are poorly built and not well maintained. If you want to ride Shasta, I would recommend spending the 30 bucks the lift ticket would cost you and get, either multiple 4 mile shuttles to the gateway trails, or one shuttle up to the Sission Callahan trail from Shasta Gravity.
As for Redding, I would recommend Swasey Recreation area, take escalator up, do an out and back on mule mt summit trail, down snail, mule mt trail back, up owens run (new trail built this winter) down enticer, then back up owens for another run down enticer or back down owen's if its more your speed.
I would recommend using Trailforks for way finding over MTB project as Trailforks is more up-to-date. If you would like someone to ride with in Redding I could see if anyone is available.