so many innkeepers get this idea ... and get thwarted by insurance and liability issues.
(sigh) i remember staying at a place as a child where you could borrow a bike or a canoe. if you fell off the bike or tipped the boat, it was your own problem and nobody sued anybody.
i can't help you with the kayak idea because we had a kayak tour and rental place across the road to partner with.
but i DID have bike tours come and stay. YES they took over the place, but they were a nice group (once i understood their needs) and we were up to four times a season when i left. nice to have that solid booking in place.
depending on where you are, look up bike tours and see if you can partner with them. also, ENCOURAGE your guests to bring their own equipment. i did have guests stay who brought bikes, canoes, kayaks and hiking gear. keep in mind, there are those serious bicyclists with $5 thousand and $10 thousand dollar bikes who will demand secure storage .. there is an old post here about providing shelter for bikes. so you have to be clear about that.
good luck!