K.W.
L.,
I'm rather new to this area, but have found a place called "My Gym" for kids. I have 21 month old (boy-girl) twins that have really been enjoying going to this activity once a week. There is one located near the Toys R Us adacent to the Fox Valley Mall. There is a one-time family membership fee, but this is transferable to any other "My Gym" location. The classes average about $17 a class (1 hr long) and siblings are discounted. www.mygym.com
I also have my kids enrolled in a music class that is great! It's called Music Together of Naperville. (Check out their web site for some upcoming summer classes, if you are interested. www.musictogetherofnaperville.com ) The music teacher, Joan Heidler, if fantastic! There are several locations. The one we've been attending is held in East Aurora (also near the Fox Valley Mall) on Common Drive at "Vocals and More" behind the Ponderosa.
Hope this is helpful.
--K.