I haven't done the Monkey on the Mainline kit, so this is a bit of a shot in the dark. But from your mention of extra molasses and a hefe yeast, I'm thinking fruit. What about a cherry or raspberry ale? Although with the intention being to combine them, one of the things you'll have to contend with is getting the fruit at a level that best fits with the porter. I don't know if you'll have time for any trial runs before the wedding. But I like the Black & Tan idea. Good luck!