If you're worried about pH and still want more cranberry flavor, you could add more to secondary. Since you're planning on a melomel, you might want to consider 71B for your yeast, and target ~1.120 for your OG...that yeast should end you in the mid 1.0teens, and give you a little residual sweetness to temper the tartness of the cranberries, especially if you add more in secondary to get some additional flavor.
I agree w/ BBBF that I'd add some citrus zest...
Packaged: Simple Cyser '14 (Nelson Sauvin Dry Hopped!)
Primary: Simple Cyser '15, Basic Spiced Cider, Spur of the Moment Graff
Secondary: Why do I keep this line here...?
Bulk Aging: Cocobochet, Wild Cider
Planned: Some sort of SMaSH. Otherwise, so many ideas, not enough time to brew them....