I don't have so much advice because I only heard about my fiancé doing it after the fact, but he's shy too and he says he doesn't remember anything (his memory basically blacked out as it was happening lol) except after it was done my dad said "so how awkward was that for you?" And then they waited in awkward silence for my mom and I to get back from the store (my mom already knew about the ring so she asked me to go to the store with her and told my fiancé that now's the time to ask).

Since you know about it, is it possible for you to be there to support him? Or does your dad want it to be between them two? I'm sure with you there it would take some of the awkwardness away.