I actually call it something other than Mommy time...
At varies times, and in all important ways, I am many thing...
Mom Friend Teacher Artist Seeker Student Donna - just me, just being (many others...)
Each piece is important, each piece brings us closer to balance. Short-change one piece and all the others suffer, because you are not attending to the WHOLENESS of who you are.
It's not nice to get out of the house once in a while - it is NECESSARY!!
And agreed, don't spend an iota of energy on whether your ex knows, doesn't know, cares, doesn't care.