Don't feel guilty about being reluctant to go it alone with your son. Just as how it takes a while for us to stop taking blame for everything that went wrong in the M, I think it also takes time to realize that we can't always be all things to our kids. There's no such thing as a perfect parent, but there are a million ways to be a really great parent. So shoot for greatness, and leave the doomed hope of perfection to the perfectionist (like my W, for example, lol).
Look at this sitch with your W's holiday as a chanca to work together to solve a problem. Tell her where you stand, listen to what she wants and is willing to give, be patient and validate, and look for a mutually satisfactory solution.
How hard could it be?
M41 W42 M 12 T 15 S10, D9, twin Ds 3 1/2 BD 1/2/2013 Living as roommates Working on D agreement w. mediator 5/13