Try Virgin Holidays or http://www.unitedvacations.co.uk They do multi-centres.

luci

Also play online with creating your own itinerary- it will be custom made for you and you may even do it cheaper than a package. To me half the fun of any vacation is the planning and the dreaming.
Start with LA- then head to NYC for your wedding -and have you given any thought to sailing from NYC down to the Caribbean on a cruise?- it makes for a wonderful honeymoon. If you're tired from your previous traveling it can be as relaxing as you wish,or high energy,,visiting lots of resorts in a week or so
Have a look at what Royal Caribbean Cruise Line, Princess cruises have to offer,theyboth do very nice itineraries from NYC. Sailing out past the Statue of Liberty to head down to the Caribbean makes for a really festive start.
Also autumn rates are especially good,after all the kids/families have gone back.