You summoned ME?
The Library has a VERY busy Summer Reading Program in the months of June and July (detailed calendar is released in May).
The Waterworks Art Museum has excellent youth art classes in the summer.
The Miles City Star releases a multi-page calendar of summer activities/events in May that is PERFECT for your needs. It collates programs from all over the community into one location.
Numerous churches offer Vacation Bible School programs that open to all children regardless of denomination.
ROCKS Program is an all day activity program (includes lunch) for school-aged children grades 1-6; tuition based, but there are scholarships available.
FREE LUNCH PROGRAM for children is hosted out of the basement of the Baptist Church (914 Palmer) Monday - Friday, 11:30-12:30.
The Miles City Area Chamber of Commerce also maintains a great community calendar at http://milescitychamber.com/events/
throughout the year.
Occasionally the Barn Players Inc (local theater group) does summer productions- visit their Facebook to stay up to date on current and future shows: https://www.facebook.com/BarnPlayersInc/
The SPROUTS program for young children hosts events. Check out their website/County Health Dept at http://onehealthmt.com/
DEAP also has events the serve families. Call their office at 234-6034.
I'm sure more will come to me... but that's a list right off the top of my head.