I don’t know your kid or your relationship with them or anything, so I’m just speaking in generalities, but most trans people I know really appreciate being called by their preferred name and pronouns. If your kid is using certain pronouns with new people or with their friends that they are out to, it might be nice to give them a try. Maybe not, again I don’t know you both, but just because someone is willing to joke about pronouns doesn’t necessarily mean they don’t actually care about them. Seems like you really care for your kid and I’m sure that if they wanted to be referred to with new pronouns that you’d be able to figure it out. Wishing you both the best.