Picking my children up from daycare during my ex's time

My ex and I alternate custody week to week during the summer. He works full time and I am off in the summer. He has chosen to put the children in childcare with a family friend’s 18 yr old daughter. I have offered to provide childcare on some days, but he has declined. Am I allowed to pick the children up from the sitter’s home while he is at work, so that I can spend time with them?

The answer to this question depends on what your custody order says.