A teacher who bribes

I have a five-year-old who doesn’t like to go independently to his church class. He will only go if I, my husband, or another adult he knows very well accompanies him. My question is not about him, however, but about his teacher. She does a good job interacting with him when she sees him, whether at church or not. She’s doing some good things to try to build a relationship with him. This past Sunday, however, none of the adults my son trusts could be with him during his class. I had him with me in my meeting, which is for the women, which doesn’t bother me. He sits calmly through the class. His teacher came to the room to try to get him to go to class with her and immediately brought out her phone to show him games that he could play if he came with her. He still didn’t want to go, and I would have said something if he’d started to, but I still don’t know what I would have said. I was kind of taken aback and am looking just for a good way to talk with her about that. I would much rather he just stay with me or my husband than go play on his teacher’s phone. I can be too blunt sometimes and I don’t want to make her feel like I’m “holier than thou” kind of a thing. Please help me be tactful. 😬 Thanks.