711 - we did this same cruise November 26 of last year. It was incredible. The ship is beautiful, easy to navigate and well cared for. Food was excellent and something for everyone. Pizza is terrific - teens will love it and available 24/7, hot deli bar, indoor buffet is tasty with many selections plus desserts, other side is usually "a taste of..." with cuisine from different areas (mexican, asian, indian, american) and the pool side buffet is more casual with hotdogs and hamburgers readily available for those not wanting to cover up from the pool.
We have 14 & 16 year old - they did not go with us - but will on next one and plenty for them to do. I would not hesitate to let them have a little more than normal "freedom" within limits. There are plenty of spots on the ship to just walk around and be entertained. If buying "packages" do it on the first day when specials are offered (spa, internet, etc.) we paid $16.50 for 30 minutes of internet time on day two - it had been nearly half price on deparkation day!
If teens are girls - make sure to attend the shopping talk - LOTS of giveaways during the talk plus coupons for port shopping - FREE diamonds international bracelet... I can't imagine anyone not having a great time!
Rooms (we had OV on upper deck) are spacious with lots of closet space - we had beds pushed together which was fine for us - but not so great if you like walk around room....beds were super comfy - best sleep we've ever had! If you have questions - just ask.