Non court assigned support modification

Divorced in 2009, custody and support was simply agreed upon, based on the difference between our salaries at the time. The kids, now 11,15,17 spend most time at moms because she live in their school district, but are welcome here 24/7. I'm moving back into the district next month and am willing to have kids live with me full time. They're old enough to decide themselves. I'm since remarried, and she's been living long term with another guy. We live in PA. Do I have a leg to stand on to re-open discussions on support, or will that tip her hand, sending her to the courts and costing me more than I'm paying now?