What a lovely, bittersweet tale!
It's always nice to see Severus in his younger years and I enjoyed this portrait of him, fierce arrogance covering crippling shyness. I also loved that he sent gifts to Petunia despite never directly contacting her again. This strikes me as being very him; he's definitely the loyal sort.
This characterization of Petunia was interesting, too. You made her sympathetic, which is hard to do given her treatment of harry growing up.
I do like that Harry and Ginny reached out to her, and that she accepted.
She really chose the perfect gift to take to them.
Well done!