Leg protection is going to do way more harm than good on the trails.
It will get things stuck in the boots and irritate the horse. They can wear out the velcro on brush and debris. They can get stuck and be unable to free their leg. Polos will get stuck or come undone and snag on things.
Don't worry about your horse's leg. Horses run and play without boots all the time. Mustangs never wear boots for obvious reasons. Besides, the boots don't offer THAT much support in the first place. Just a couple percent extra. Polos even less, splint boots are just there for overreaching. Unless you have a total basket case horse who trips and steps on themselves every stride, don't put boots on the trail ride.
If your horse isn't sound enough to be ridden without boots either, then you have a whole other problem entirely.
Pssh.I didn't pick up the wrong lead
It's called a counter canter...
...A very advanced maneuver.