Ex wants to move 2 hours away - what are my options?

She got a job offer in Seattle and wants to relocate with the kids. Our custody agreement says mutual agreement required for moves over 50 miles. Obviously I don't agree because that cuts my time in half basically. Our lawyer says I can contest it but that's gonna be expensive and messy. Has anyone dealt with this? Do I have actual standing to say no or is this one of those situations where the court might side with her anyway because of 'stability' or whatever. The kids are 10 and 8, so not old enough to have a preference that matters.