I would brew and ferment the beer portion first, then add the grape concentrate after the primary fermentation finishes...then let it finish out and continue as you normally would.
Packaged: A bunch of random stuff...*and* American Pale Mosaic SMaSH
Recent Meads: Mead Day '11 Ginger Metheglin, Mead Day '12 Traditional (orange blossom) Mead, Fresh Simple Cyser '12
Primary: Hopefully being refilled next week!
Secondary: Why do I keep this line here...?
Bulk Aging: Cocobochet
Planned: Hop Metheglin #3 (NZ hops), Trad. Gesho T'ej