Hi 4get,
A very personal decision to be made here, but if it's playing on his mind that he feels he needs closure and wishes to see her, as not seeing her would possibly bring regret that he did'nt go for the rest of his life, then I would say for him to go.
If it were me....same position.......even though there is NO excuse for being abandoned at such a young age, i would think hard about going........as after all she is his biological mother.
Best of luck on what he decides to do, 4get and best wishes to you both, sweetheart. :0) x