We stayed at several hotels in bkk with kids starting from very early age
Among spg, ROS is much more practical with kids - on the river for fireworks (most spectacular viewpoint from the room i ever had) and tours, a reasonable upsell to suites, good family pool and another one for adults etc etc..
other properties being in the middle of concrete jungle in high heat with kids offer littlle appeal aside from easy access to malls and bts even though they are a bit more upscale