What an exciting event. I really don't think it would be awkward between the Deleo's and Slash, actually quite the opposite. If they do converse, they would probably ask about how each other's bands are doing and how happy they are they for one another.
I wonder if this will be televised. This is something MTV or VH1 should broadcast, but because MTV (aka MUSIC Television) and VH1 don't play MUSIC anymore, I bet I won't be able to see it.