I've got a fungia that can eat its food fairly fast, within a minute or two so something like that you won't have to guard very long.
Not sure how fast your trumpet, brain, etc will eat but you may have to sit there and guard its food for a little while.
My tank currently has no inverts like shrimp because I feed my dendros almost daily and would be ****ed if the shrimp stole the coral's food.
You also may not have to feed your corals because they are photosynthetic corals and really don't need to eat. I don't think you want to be doing this a few times a week as it may be time consuming, since a lot of the corals energy comes from light, maybe you can just feed them once a week to supplement.