We are trying to arrange a group family holiday for a big birthday for one of my parents. There will be 8 adults and 5 kids in total (ages 3-9). It needs to be around Christmas time (2018) due to school holidays and we would like somewhere warm with nice swimming. Ideally easily reachable from UK, north America and Australia (although we appreciate flights might be long). We are willing to splash out but want to keep costs as reasonable as possible (if that makes sense - I.e. no private islands!). Ideas so far: Mexico, Costa Rica, Carribbean. Any suggestions?