Has to be the Canary Islands!!! Generally the weather in March is hot and sunny during the day but cool enough in the evening to get a decent night's sleep. There's plenty to do to keep two teenagers occupied (my kids are 14 and 16 and they love Tenerife and Lanzarote in particular). We're off to Fuerteventura next Easter, we were in Gran Canaria this Easter and I'm thinking of booking Tenerife (I love Tenerife) for Easter 2008.
As far as avoiding hidden charges - it depends on whether you want a hotel or self-catering. If you're in a hotel then usually any children over 12 pay the adult price, so you'll be paying for 3 adults, but you'll probably get 3rd adult discount. If you go self-catering the child prices usually go up to age 16, but you'll have to pay adult price for one of the kids to get child discount for the other one, and then you'll probably have to pay ridiculous under-occupancy supplements, so it's sometimes cheaper to just pay for 3 adults to avoid these supplements Believe me, as a single parent I've spent a long time wrestling with 'hidden charges', and now I just find it works out cheaper for us as a family to go all-inclusive as 3 adults and know that everything is paid for.
Good luck with your choice

....have you thought about going the diy route for value..most apartment prices are just that, for the apartment and not per person....flights can then be planned to suit your own preferences and budget. if you're going somewhere where eating out is relativly inexpensive, ( such as...oh, Tenerife ) and where the climate is great in March ( oh...Tenerife again..) then a good holiday is assured....

I would suggest Red Sea area of Egypt. Its good value, and there are lots of large resort hotels with 2 double beds in the room, so you could all go in together, without being to cramped.

Also with Sharm the both the AI deals are good value, but if you decide to go B&B eating out is really cheap.

You proabably need to be as close to Namma Bay as possible, as this is where the hard rock cafe, camel bar, etc are. The tour ops also do the usual trips, quad bikes, trips into desert, camel rides etc, and if you are feeling really adventurous (and have the funds ) you can do a day trip to cairo to see the pyramids.

Good Luck.

thanks for the replies.i have done holidays diy route before when whole family going and it has always been cheaper and better quality accomadation.But booking for three for just one week being school holidays the flights are as dear as a package holiday
unless people know the cheaper places to look for flights.I looked on sky scanner flights for 3 come to about £750 to tenerife