This is for a family without children or with older children:
You can see the old Baden in under 2 to 3 hours topped with a beautiful promenade on the Limmat where you can dip your already sauna-ed footsies in the thermalbank (free thermal foot bath on the Limmat). Then go eat dinner at the posher Chinese restaurant "The Smiling Fish" next to the train station. If you lived in N America, you'll understand why the "posh" qualifier. Of course, the food is Swiss Chinese, but the cleanliness is Swiss.
There is an artsy movie theater, right by the Postautostation.
Brugg is very tiny, the "old town" is "the old street".
If you like to walk, you can go to Turgi by train/bus, and then walk to the Wasserschloss, where the Reuss goes into the Aare - about 3 Km.
Have fun in the exciting Aargau!