Does the custodial parent have say so in child care?

I have full custody of my son and his mother is getting alternating week visitation during the summer....my son is 4 and he is not even in school..so does summer visits apply? Also her job hours are m-f from either 3:30 -11pm or 4:30 - 1am....now she wants to keep him during that time with a babysitter and she doesn't want me to pick him up when I get off work at 6. Now this is time I could be spending with him and be putting him to bed, not a stranger. Please help give me some advice!