Custody schedule adjustment - thinking about asking for summer weeks

Current setup is every other weekend plus one weeknight dinner. Kids are 6, 9, and 12. I work in tech so I've got flexibility in the summer and was thinking about proposing I get them for like 4 consecutive weeks so we can actually do trips and not just have every-other-weekend parenting.

I'd obviously make sure their mom still gets significant time. How do I even propose this without sounding like I'm power-playing? My ex is usually reasonable but we have to tread carefully.