L.J.
I wish we knew the age of the child and the frequency of the visits with dad that has been established, every weekend/every other, etc. If he's young, that would make him maybe want to stay with mom but if he's older, he might just prefer to stay in his regular routine. My parents always worked out the details that would suit me best to keep me happy which they were determined to do for my benefit. I was 4 and would only visit for one day (no night) each weekend (maybe 9-6) and that worked well, then as I got older it was everyother weekend from Sat. 10-Sunday 5. By the time, I was about 10-12, I was involved in lots of school activities and would tell my dad on the phone that I couldn't come because I had plans with friends. He wasn't ever happy and would sometimes fuss to my mom, but he let it slide and kept paying child support. Mother would insist that I go at least once a month for a weekend and I would always have a good time so it was good for us all and kept us close. See if you can work out something with the son and dad that will help them to stay in touch but maybe work better.