This is a wonderful atmosphere to take the kids to for fun. The Children's ExpERIEnce Museum is not only nicely priced for a family but I highly recommend getting the family membership if you think you might even go one more time. I guarantee, if you leave it up to the kids you'll be going more often!
They have great science exhibits that are hands on. Geared towards children ranging from about 3 or 4 up to at least 10, kids of all ages will enjoy the various projects, learning about science in a fun way. My kids loved the bubble exhibit when they were small and of course the dress up area where you can pretend to be anything you want. Wegman's Market provides a wonderful and realistic grocery shopping experience for both kids and adults to participate in. Tons of fun for hours.
The Erie Art Museum is very hit and miss though. While it can often boast some great works of art and entertainment, there are often long periods of nothingness when they're setting up for the next exhibit. A few exhibits are there all the time, such as the very life like miniature city and the photo/portrait exhibit of local Erieites to remember from various eras. They do have a 'free' day when you can give a donation for the visit and I highly recommend calling ahead to see if they have exhibits running before you go.