Can a father send a family member to pick up his son during his scheduled visitation time?

I've began a new job which requires me to work swing shift (2 PM- 11 PM Monday through Friday). I really don't want to lose a night and Saturday morning with my son considering I only have him every other weekend throughout the year. My ex and I are not in good terms and I'm sure she's going to make this very difficult for me. My question is if it's legally okay to send my child's aunt, grandparents, or step-mother to pick up my son Friday night for me so I can at least wake up Saturday morning and spend time with my child without having to drive 45 minutes to pick him up and another 45 mins back to my home. Does my ex have the right to refuse this request? Does all parenting plan include the right to first refusal or is that something you'd have to request in court? Would I have to modify the existing parenting plan if my ex refuses to let my child go with his aunt, grandmother, or step-mother? Does she have the right to refuse or would that be consider breaking the visitation order?