I have shifted into reverse about 3 times doing the same thing since iv been hypermiling, It has not done anything to my car. The first time it did absolutely nothing weird, going about 5mph (8kph) , one time I did it going about 40mph (64.3kph) and the car jumped a bit but I put it in neutral and it worked just fine. Once I did again at about 40 (64.3kph) and the whole car cut off, I pulled over and it cranked right back up and drove perfectly fine... You will be fine
BTW~ I reverse into my parking spot, All 3 times were no problem at all