I have recently finished a summer volunteering in the Ronald McDonald House's Art Therapy program. It was an opportunity I savor and regret that I had to leave due to a conflct with my Fall Semester schedule. They are currently looking for a new volunteer for either Mondays or Thursdays between 1 and 5pm. As a volunteer, you assist the Art Therapist and help children through art projects. This is a great way to get experience with children, whether for a career in art therapy, childhood education, art education, or whatever else. It is really fun and I hope I can do it again during the spring semester. The RMDH is in Wauwautosa across the street from the children's hospital off the 10 busline (and some other buslines), so it's a bit of a ride via public transportation, but I've used the bus all summer. However, if you have a car it should be no problem at all.
Feel free to leave a comment if you're interested. I will gladly give you more information.