How long you thinking of going to Chaing-Mai for. There is plenty to do for a few days, such as elephant trekking, river rafting, visiting numerous temples, night markets, shopping, going to hill tribe villages etc. Whether these will be of interest to teenagers I would leave to you to judge. You can always do a multi-centre with a Thai beach.

Have a look at http://www.asiatravel.com/chiangmai.html to get a feel for some of the hotels. Some of these will have family rooms and suites.

Not sure if this is still relevant as you posted in October, but I was in Chang Mai 5 or so years ago and loved the place.

I was travelling with a mate so dont know about family rooms but travelled up from Bangkok by train and were met by a number of people giving advice on treks, one of which we took up. I think this was a two day trek into the jungle staying overnight with a family and the trip included a raft along the river (made by the guide), and elephant trekking. This was excellent although you need to be fit.

Our other excursion was a trip to Chang rai and across to Myanmar ( Burma) and Laos by boat. Again a memorable experience and much better than lying on a beach all day.

I adored Chiang Mai. We stayed at the Royal Princess Hotel - right in the heart of Chiang Mai's fab night market , would love to go again as there is so much to do, we went there 4 years ago and I believe the ity is growing at an alarming rate, I would go soon to capture the rural charm that attracted visitors there in the first place , shirleyV