I brewed a couple of AG batches with a buddy for his wedding. If you haven't done AG yet, give it a couple of tries first to get your head round the process. Anyway, after thinking it through, we factored in a few consideration:
(1) Brew for the guests, not yourself. Something light in colour and body, not too strong in ABV or bitterness, and clear. The wedding demographic aren't going to appreciate a smoked Imperial stout or a screw-your-face-up American hop-bomb.
(2) Personalise it. My buddy is Australian, his wife German and the wedding was in Cambridge, so we did recipes that mixed Australian and German ingredients and techniques. We settled on doing Greg Hughes Spring Ale but subbing for Galaxy and Hallertauer Hersbrucker hops, and we did a pseudo-lager with Summer hops. Galaxy and Summer are Ozzy, Munich malt and Hallertauer Hersbrucker are German, and Maris Otter was developed in Cambridge.
(3) Keg, cornies if possible, but we used King Kegs. Guests aren't used to bottle conditioned beers and would just glug from the bottle. You don't want a queue for the toilet. This was the first time I used kegs, and unfortunately the pseudo-lager leaked, had to be reprimed three times and was flat and nasty in the end. We didn't serve it. The Galaxy one was great though, and didn't last long at all.
(4) Think about how it will be stored and served. Moving a full batch in a keg will stir up less sediment if you have to move it. We were lucky in that we could keep the keg in the catering fridge at the venue and didn't have to move it very far, and it was kept cool in the shade, so was nice on the hot summer day.
(5) Make sure the venue will allow you to serve homebrew. Many won't if they have a bar.