Hi my family and i are planning a holiday for next June. As a family we have been to Thailand, Singapore, New Zealand, Kuala Lumpur and Bali. We prefer a destination with a warm climate. Our kids ages are 12, 17 & 15. Any destination suggestions would be appreciated. thanks
How about Italy, Tuscany and Rome?
More things to do and see than you can shake a stick at - Culture, food, history, scenery, weather.... the list goes on.

Given the age of your kids, i would suggest Bali or Penang or maybe somewhere adventurous like Sabah and/or Sarawak (ie, kids would be old enough to climb Mt Kinabalu). Haven't been to New Zealand but there are lots of opportunities for adventure there too. Australia also good (assumign you are not Australian).

we are considering Sri Lanka to go to with our (much younger) children.
I'm sure it would be very interesting for older children as well. Very diverse in activities and beach time as well.
You can visit the cultural triangle, hill villages with tea plantations, you can do rafting, climb Adam's Peak, go for a safari to spot animals, plenty of beach time ...
Penang is a great place, but not so for beaches. There's other great stuff though, such as great architecture, and natural beauty.
Hi! We are loving Central America! Panama is relatively cheap, new cultures and languages, safe, and warm. What kind of experiences are you most seeking that would interest your kids? Rainforest exhibitions, volunteering with rescued animals or local children, learning a new language? We did a bit of all of that. For starters, if you think Latino culture may interest them; maybe show them some travel blogs of people who have been there with their kids (any age really) and see what excites them. On our site, we have a great volunteer wit the locals video on the sidebar and another volunteer with animals one (under the 'videos' tab), So, if Latin America is an option at all for you guys, you're welcome to browse through the entire site with them- it's packed with pictures.
Good luck!
Have you ever consided Isla Mujeres Mexico? The anual Whale Shark festival is being held this June 21-24 and is suppost to be incredible! I can tell you that the Island is beautiful, amazing beaches, and very safe. Our kids love it! And your kids would too as it is very safe for them to explore with you, or on their own. So much to do there, from fishing, snorkelling, sunning on the white beaches, viewing ruins, the turtle farm, dolphin descovery, garaffron park (zip line, kayaking, etc) and more. You've probably already decided on a location, but if you want more info let me know!