Go to Lenzburg. There is a castle nearby (very European and unusual for someone from the US) and the old town is pretty. Shops will be closed but you can still wander around are there are some nice cafes as well. check what is open on the internet.
Also there is a Foxtrail. Don't know if you know they concept but it's riddles that you have to follow in order to know which side you have to go (like an elaborate Schnitzeljagd). Is done in little groups. Really nice. Riddles will be in German so at least someone has to speak German. You will also enter the museum on the castle (can visit the whole museum after which is pretty good). We have done that with friends and had a great time http://www.foxtrail.ch/de/trails/aargau/schlosslenzburg
Another option would be the Stapferhaus. It's a great museum and at the moment they have an exhibition about money (very appropriate for someone visiting Switzerland) ;-) where you can jump into a huge mass of 5 cents pieces (baden im Geld) http://www.stapferhaus.ch/ausstellun...e-ausstellung/
maybe call them today to ask if they are some explanations in English. I have not yet been to that one but went to the last one and if I remember right there was information in English.
Also Baden is a nice little town. Or closer to Basel but still in Aargau is Rheinfelden. There you could cross the bridge and enter Germany. Might also be interesting for Americans. The concept of having no border control usually is very foreign for them (unless they have lived in Europe before). If you go to Rheinfelden, there is the old town but there is also the Feldschlössschen brewery. They have guided tours on Sunday. http://www.feldschlosschen.ch/de/03_...htigung_01.php
Check with the restaurant maybe if you can still join (it says Friday on the homepage). Also the restaurant offers a brunch which is supposed to be nice. I have not been to the brunch but have eaten twice at the restaurant and it is nice!
One last option would be Augusta Raurica. It's an ancient roman theatre that can be visited. Might also be interesting for someone from the US. http://www.augustaraurica.ch/de/
As usual all are accessible by public transport but if you have a car you could even combine two out of these.
Have a good time!