I was always a rider, not a driver when first getting into horses. I than decided to try my hand at driving and absolutely loved it. Now I would rather drive than ride. I was lucky and found a trainer who drove by horse and buggy/wagon everywhere. He knew alot of the amish. Told me I took to it like a duck to water. But again, been around horse's, and knew the dangers. It was alittle scary at first, as you don't have the use of your legs to help cue the horse, all communication is done thru driving lines and voice. It can be done, just takes time and a willingness to learn.
My trainer started me with a trained driving horse, than as my skills progressed, we went to horse's with less training. Not all horse's make good driving horse's. Your haflinger would be plenty big enough to pull buggy, just have someone evaluate your horse to see if he's a good prospect for driving. Want a very level headed, forward driving horse.
My driving horse is haflinger size and we go to town and back with no problem and town is about 13 miles away. I bought a horse with driving experience though. He was 3 1/2 yrs, old and gentleman had used him to go to town and back for groceries. He lived in a small Alabama town.
Have put alot more miles on him since getting him in the last 2 1/2 yrs. I've owned him and he is a great driving horse, not much of a riding horse, but great at driving. Horse's sometimes have a preference, and will let you know which they prefer. LOL Some are good at both.
So, find you someone willing to show you the ropes and get started, you will love it. If you don't you can always go back to riding - just can't carry as many groceries. :)