I like your website mock-up - and it's an interesting idea to include those extras. I see it on hotel and airline websites all the time. Even if someone didn't take advantage of those services, it still appears to offer a more full-service experience to the guest.
We already have a page on our direct website with links to various activities, tours, grocery delivery, etc. But to try to make a commission from that would require a LOT of work in contacting each of those "partners" and somehow coming up with a way to get paid - and then hope that they will pay you (or do you charge them and then pay the tour company, for example?).
I've also wondered about having rental items for offer, like kayaks or snowshoes, or perhaps cribs/playpens - I haven't done that because it might seem a little "grabby". And some people might think that it should be included with the rental. Also, if someone were staying a week how do you know which days they are using your product if nobody were there on site?
If one were to sell their own product (i.e. a gift basket) it might be the best way of making extra cash, but I question if the hassle of arranging tours, etc and collecting a 10% commission would be worth the hassle.