I think I might be confused. Please forgive me if I am.

I assumed by the title that this was a child who was celebrating his first birthday, and you want to do something lasting and fun so that you and he can see it every year on his birthday.

However, reading other replies, I think I might have taken it wrong. Is the child deceased? I'm so sorry if that is the case, and for my misinterpretation.

However, in either circumstance, I think planting a tree is a wonderful idea.