Mommy is not as fun as grandma

I took the kids to the park today and grandma came with.  I had one of the kids in the swing and the other one was playing with grandma.  When she was done swinging she said "mommy I am going to go play with grandma and sissy you can play with someone else."  You would think that would hurt my feelings but really I would rather grandma be more fun than me, then they will want to go to her house more and mommy can get some free time!!