What's the right amount of time for transitioning a 2 yo?

Hello everyone! I'm new to this group. I'm so excited to join all of you and to read all of your posts. My husband and I are in the process of transferring a 2 yo into our home. The child is doing great. We were doing day visits with the family who currently has custody of the child. The child decided to go from one day visit to not wanting to leave us and have a sleep over all in just a few visits. For a few weeks we started with the child just sleeping over one night every weekend, along with phone calls and FaceTime. Just recently we added Friday and Monday and everything is going wonderful on our end. No behavior problems and we even started potty training and its going fantastic. The last three drop offs that we have done for the child to go back to the caregiver has ended with crying and not wanting to go back to the caregiver. This Monday afternoon was so hard. The fit that the child threw to go back to the caregiver was very upsetting for my husband and I. The caregiver wants to get a child psychologist involved to help with the transition. However, I don't know if this is something that is necessary and if maybe we should just move to more time with us and maybe weekend or so with the current caregiver. This is all new to us. My husband and I don't have anyone that we know that's adopted or fostered children to turn to for advice. We want this to go as smooth as possible for the child. If anyone can help guide us and let me know if it's needed for the child to see a psychologist or if this is just something for the caregiver who is having a hard time because the child is adjusting so well and wanting to stay with us. We have even tried to stress to the current caregiver we want them to be a part of the child's life; monthly visits, phone calls and facetimes whenever, be around for birthdays and holidays.