I would think you could get retrospective approval for installing properly insulated wooden floors, because the Owners Corporation cannot unreasonably refuse a renovation request. Have you checked to see if your floors are noisy? Talk to your neighbours, and visit there, while you get your wife and kids to walk around on your floors. If you find a problem, then there is one, and it’s your responsibility to fix it.
And I have to agree that letting your kids practice with musical instruments in a Unit seems, perhaps, a trifle unreasonable. Electronic keyboards can have headphones! Excess noise issues come and go – you need to deal with the current problem. There is unlikely to be negligence or incompetence in past strata committees – it was your responsibility to recognise the potential problem with noisy floors (& musical instruments) when you bought the Unit, and you failed to check if there was any renovation by-laws in place. In a strata building you are part of a community, and so you have to consider your neighbours.