Malaysian Borneo (Sabah)......
Long flights - we went London-Muscat-Kuala Lumpur-Kota Kinabalu (you could go direct London to Kuala Lumpur, but this was the cheapest).
Flew straight on to Sandakan with Air Asia (around £25 return each) and stayed 2 nights in Sepilok. Visit Orangutan Sancturary, Sun Bear Sancturay and Rainforest discovery centre.
Lots of people to do all this in 1 day, but we enjoyed going slower and also enjoying the swimming pool at the hotel.
Then moved to Sandakan and on to a 2 night-3day homestay in Abai Village in the rainforest of Kinanbatangan river. You can stay in guest houses in other villages instead, but this was a real highlight. Food amazing, no shops, very relaxed, access by boat only. Guide took us out wildlife spotting each day and we saw orangutans as well as zillions of monkeys, birds and more.
A day in Sandakan - non touristy city which we all enjoyed more than expected.
Then to Kota Kinabalu (main city) before spending 4 nights on Mantanani island - snorkelling, swimming, relaxing. Very very basic - reviews are mixed, but if you expect basic/rustic/1 hr boat trip from land so random food supplies, not an issue. We very much enjoyed this.
Final 2 days in Kota Kinabalu - 1 day on an island in the marine national park there including the longest island to island zipwire!! We all did this.
Then last day went on a white water rafting trip with riverbug which was loads of fun and ended with huge hot buffet lunch.
We did it all ourselves - spent £1700 pounds all in (not international flights of course) for 4 of for 15 days. Island and river more expensive, rest of accommodation was backpackers costing about £25 per night.
No-one was sick, no hassle, food great and cheap, easy to get around - taxi's are cheap, airports have official taxi counters so getting to hotels on arrival was just as easy as if we had booked a more expensive transfer.
Kids aged 8+.
If there is anything you want to know, just ask! (Excuse long post too).