Don't worry about it, they are used to it!

When I went to get a bike a couple of years ago I hadn't been on one in years!! I was so worried that I would fall or crash or do something stupid. I wobbled a bit but managed to do just fine. Just let the staff know that it has been awhile and don't be afraid to ask questions about how things work on the bike if you need to!

As a fellow horse rider, I know what you mean about the difference between falling off a bike vs a horse. I also think I would rather fall off my horse anytime then my bike!!!