I see summer as a chance to make up for not homeschooling.
Most of what we do looks like unschooling where I play the supporting role to their interests by taking them to the library, getting materials for sewing, finding the horse riding lessons, etc. The part that's more structured is math and I require they regularly try problems that make them think.
DD8 is working on long division and she's felt some frustration. The lightbulb went on today when I realized she's interested in sewing so I presented it as, "If you have 200 yds of fabric and it takes 12 yds of fabric to make a dress, how many dresses could you make?" She still made some mistakes but the difference was her attitude. She wasn't frustrated and wanted to keep trying. I can't expect a teacher with 25 students to do this so I'm glad there's summer!