If it is just to write at the head of a farewell card for your friend, then [your friend's name]へ is fine.
The name part is up to the relationship between you and your friend, and age.
If you two are very close friends and you're both at school, you might write [name]ちゃんへ (if your friend is a girl) or [name]くんへ (in case your friend is a boy), for example.