Dear Gordon,
Thanks for your question. We have several tours to discover the islands by bike, and what I can't tell you is that we can always adapt (even during the tour) to your desire and physical condition. In a general way Terceira island is not a very flat, but we have some areas where we can design relaxed tours. By other hand we never run our tours in a rush, so "technically" everyone can do it as long as you have some training (even if in some parts would be necessary to carry the bike by hand).
The 3 days bike touring around the island is classified as a medium level, and you need to realise that you will bike 23km first day, 45,9Km second day and 30,6Km on the last day... it's not to much, but specially on the second day you will have a certain distance to cover... but if you are road cyclists I'm sure it will be not a problem for you.
Please let me know if you have more questions, or please write us directly to info@comunicair.pt
Thanks and I hope to you soon on Terceira! :)