Hello there, we just got back from a 4-day vacation to Bangkok. It was the first vacation with my family of origin, yes the whole jean gang! Dad, mum, elder sister, younger sister, brother-in-law, niece, KW and our two boys... With 3 kids under 5 years old, you bet it was a chaotic at times. That said, I think we all had a great time. We co-existed for 4 days with zilch drama or blow-ups (very usual for a family full of headstrong women).
We stayed at Centara Grand Centralworld, which was hands down ridiculously convenient. Best part of all, we scored a surprise upgrade to their Executive Suite (oh, the suite life), which was godsend with you have two incredibly energetic boys.
Though I normally like to stay in Singapore during December (cooler weather, less people), the Christmas decorations made the city and hotel really festive. And boy, did our boys love those reindeers.