Havelock is Heaven, there ain't doubt about this.
If you are looking at best deals, try Cocunut Grove. It is relatively new place but very affordable. Rs 500 for a cottage; Rs 300 for a room. The staff there are ultra nice.
Activities: Rent a bike (200Rs + petrol cost), chill at beach, check out corals, deep sea dive, boating etc.
Food: They have everything and are flexible; so you can have your choice; you can cook too if you so desire. There is a place (wild orchid) for better food.
Cleanliness: Pretty good.
Distance: Once you reach Havelock island; autos would take 30-50 rupees (its 3 kms from the jetty)
To reach: You have to book tickets once you land in Port blair; which is bad. There are some agents who would charge a premium for ship tickets to Havelock. You can try helicoptor ride (Rs 850 per head) which is ultra nice. It takes 20 mins of breathtaking ride. From ship, it would take 2 hours.
Also: Check out Neal island (on way to Havelock).
Kids: Not very attractive for kids. No place where you can leave kids.
Oldies: Can't expect luxury. Tourists are dressed shabbily; might look weird if you are with your parents.
Overall, its amazing! You would love your every moment; we did! We are even planning to time share a cottage on a permanent basis.