Like you, I had a 20+ year break in biking. There's a reason people say "It's like riding a bike" when they refer to something you can't forget how to do. After a few rides it will be like you never quit. I don't fall often but I've had a bike squirt out from under me on ice a few times. As long as you don't stick your elbow out or make other instinctive attempts to stop your fall you'll be fine. Keep your elbows pinned to your side, feet on the pedals, hands on the bars and ride the bike to the ground. A helmet will keep you from banging your head. Gloves keep your hands from getting cut up. Get up, brush yourself off, laugh, continue riding.