There are three networks of children’s museums in the U.S. ACM, ASTC, and NARM. (If there’s another that I missed, please let me know at email@example.com).
Belonging to a network means you can go for free or reduced entry to any other museum in the network. We’ve saved many hundreds of dollars by joining. Typically, the cost of joining one of the networks is $20 or so in addition to the cost of an annual membership at one of the museums in the network.
We frequently go to children’s museums when the weather is wet or cold, and it can be a great way to have a playdate without having to mess up the house. And then when taking road trips to the grandparents, we will look for a museum on the way that is in one of the networks, and we go for free.
ASTC (pronounced “Aztec”) is the Association of Science-Technology Centers. The ASTC Passport Program is similar to the ACM one, though the focus is on children’s science museums. Their list of 364 participating museums is in a PDF, current as of 2017
The NARM (North American Reciprocal Museum) Association is another network, much larger than the other 2, with 896 participating museums. NARM includes many historical sites and other kinds of places beyond the STEM-focus of ASTC. Use the NARM interactive map to find museums near you, or look at their PDF, current as of 2017.
Look at these three networks for a children’s museum near you (some museums belong to more than one network) and see if there are other museums in the same network you are likely to visit, e.g. near a relative’s home. You may be surprised at how many children’s museums are out there. Many have limited marketing budgets and don’t advertise much.