We would highly suggest trenching and treating instead of only treating inside the cinder block wall. Termidor is meant to bond to soil and be applied into the ground. It will not last very long just treating into the cinder block walls. Cinder blocks are also very porous, so they will soak up a lot of the termidor and you might get a few months of protection instead of 10 years when applying it into the ground.
You should follow the instructions as outlined in our How To Do A Termite Treatment article to treat the exterior and underside of your crawl space.
Termidor SC bonds to the soil and does not move once it is applied. Therefore, it can be applied where a well or garden is present as long as it is more than 10 feet away from the well or garden or tree. We would suggest not applying Termidor SC along the side of the house that is within 10 feet of the trees. You should keep a close eye on this area of the house for termites, or you can of course always install some Termite Bait Stations in that area for monitoring activity.