Needing opinions on whether or not I’m TA.

I’m a single dad. Friday my son is receiving an award, and as part of the ceremony, he is supposed to write a letter to his instructor for helping him achieve this, and also to any family member he wants to write one to as well to show appreciation for supporting him.

His grandmother has been the main person to take him to his classes since he started, with me being the second person who has taken him the most.

His mother and I are not together and have not been since he was a toddler. Since he started taking these courses, she’s taken him to maybe five classes since he’s been going for the past 7.5-8 years. If it was ever her time with him, her mom was the one to take him. Not because she was working or anything, just because she was never up to taking him. There have been numerous times over the years if I’m off work, even if it’s her night with him, I’ll come get him to take him to his class, then take him back to his mom afterwords.

Where I’m getting with all of this, is that he notices that his mom does not participate in this at all. So would I be TA if I didn’t make sure he wrote her a letter thanking her? I’m not telling him not to and would never tell him not to, but if he decides in the end not to write her one, would I be TA for not insisting he does anyways?