I congradulate your dad on his decision. I just bought my dad a PUCH mixte that is pretty cool. I got it because he said he wanted to ride but did not want to be in the bent over position all the time.

I was glad to find this bike and I think it will be something that can be adjusted to his needs for comfort. You might just show your dad all of the different types ie Hybrid/Mixte/Road/Dirt bikes and let him figure out what he might be interested in as time goes on. Mention to him how important comfort is to the enjoyment of biking. I bet he will figure it out.

Link to a pictures of the PUCH mixte:

http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWAX:IT