Reading the thread was going to suggest looking at Bintan Island as well. We had a few extra days on a longer Hong Kong - Singapore trip several years ago (just before the pandemic) and my wife wanted a break. Caught the ferry and spent a few days at the Club Med on Bintan Island and it was great . My boys 9 and 3 had a great time. My wife and I liked it enough we are trying another Club Med family oriented place this winter. Beaches not be as nice as other places mentioned but very easy to get to and you can get a little exposure to Indonesian culture. Club Med is probably about $600/night for your family but perhaps when you consider the savings of not another flight and all food included, it could make sense -- or if you can find a deal. Or take a look at other hotels on Bintan Island.