Clean tub while you are in it. Mark height of water with tape during bath. Next time, take shower with tub stopped and compare water level. Don't waste cold water Stopper tub before turning on water. Initial cold water can be warmed by adding hot water later.
Small kids can go in together.
Replace worn washers, O-rings, packing and faulty fixtures. Make sure faucets are turned off when not in use. See how light a spray you can wash with. It is not necessary to shower longer than five minutes. Remodel with low consumption shower heads.