Pine flats is a less traveled to hotsprings destination. There are only 3 pools and two are located on the mountainside overlooking the river and the third is located down on the river (when the river is high, it washes out). It is a bit of a dangerous hike down to the last pool so not a great destination for kids. Make sure to bring headlamps if you plan to go at night.
Kirkham is by far one of my favorite spots, especially during the fall and spring. The gate entrance closes during the winter but you can still walk in and access the natural hot springs. If you’re visiting Idaho, this is a must see! the hotsprings waterfall into small pools alongside the ice cold river. The only downside is that it can get very crowded on the weekends.
Arrowrock is a great and easy weekend get away. It’s only about 1.5 hours from Boise. It can get very crowded on holidays and weekends though so try to arrive early. Most people just camp out on the beach wherever you can find space. If you have a boat you can put it in the water right off the beach and camp next to it.