I think your friends would more appreciate the effort and cost you are going to to share the day with them, rather than the gift of money you bring.
We didn't live together until aobut 4 months before our wedding, but we were totally set up at our engagment (where we so didn't expect to be given gifts. WE still have stuff in boxes at my parents coz no room in our unit for it!
So, we decided to do teh honeymoon registry, guests didn't have to say how much they put in and the travel agents did't tell us individual amounts. We did still get gifts on the day as well, which we appreciated just as much. So if you go the route of getting a gift, I'm sure they will still love it. You could go for something more ornamental than practical - say, a nice vase rather than a platter dish - the Willow tree ornaments range have some lovely ones suitable for weddings or engagements, and they have little meaningful quote to go with them. We got one for our engagement, and have since bought a number of friends similar for weddings or such, just because they are so nice. (they also don't cost too much - around the $40-$50 mark, but they look lovely)