Please get out and about use the local shops and facilities, enjoy the local bars (they are like nothing at home), there are some great restaurants in spectacular settings nearby, visit an orphanage, take a tour of Mombasa Town, etc. You will end up having a rich and varied holiday with some unforgettable memories and you'll probably catch the incurable disease, Kenyaitis.Lots of tourists who have taken this advice and gone out and about are so glad they did, then they go back to the hotel and shake their heads to find most people haven't left the poolside.

Have a read of the FAQs on the right of the forum page for lots of good info about things to do in the area, bars, restaurants, etc and a map to show where everything is . One specific thing as you can't lie on the beach in front of the hotels at Bamburi because of the beach boys, if you want to lie on the beach turn left, walk for about 15 minutes and Yamas beach bar has loungers on the beach and no beach boys, you just have to buy a drink or two. Better still call Monsoons restaurant, get them to send a (very) cheap taxi for you around midday, use their loungers and have a swim on an empty beach then have a long leisurely lunch of great food, and stay and chill by beach until the sun goes down.

Go and have lunch on the floating restaurant on Mtwapa Creek, or go and have a romantic dinner under the millions of stars on the bank of Mtwapa Creek with the boats bobbing in front of you. Both will send a free  minibus to pick you up and drop you off at your hotel.
PS don't let reps influence which orphanage to visit, there are tales of dark deeds involving reps and their advice about orphanages here