I have put several miles on Yamaha (Giant), Shimano and Bafang and a few on the Bosch. The tiny front sprocket on the Bosch made it the worst of the bunch to ride with a dead battery. The normal ---38-46 tooth chainrings on the other mid drives work better when dead.

Your guys will be able to cruise at 17-20 mph easily with ebikes. With a 100+ load in a trailer without electric boost it would be more like 10 mph.

I would stick with 2" wide tires, front shocks, suspension seatpost and disc brakes---I like the simplicity of cable brakes but hydralic discs are barely more expensive and I doubt you will find any good ebikes without them---Run from any ebike without disc brakes---.