Most kids his ages would be crushed and devasted if their friend didnt go.
They dont understand ''the principle of not going'', that doesnt mean squat to them! He's 7, NOT 14.
I would ask him how he would feel if I did not go. If he even hints that he would be hurt, then I would go.
He will see you not going as a personal rejection. Kids take their first talk very seriously. I honestly think he take it personally
The one suggestion to just go to his talk, and then leave right after sends the message loud and clear that you went for the boy, and nothing else.