Many years a go I was coordinating a group of developers that was somewhat larger than yours and possibly even more distributed. E-mail and phone conferences were fine, but they were no substitute for face-to-face communication. At some point I just decided that we all needed to get together for a 2-day meeting every month, which meant everyone else had to fly in, except for those in Asia, who joined by videoconference in spite of ridiculous time zone differences. No objections from upper management. It definitely helped (and later learned that people regretted when I stopped holding the meetings.) The key is to make sure you work in a place where it is a non-stop flight for everyone else.
At the moment I am working on a project where the center of activity is two time zones away. Coming up on a review, I realized that there was a big disconnect in how the people in charge thought my part of the project would work - this in spite of our having even more advanced online collaborative tools to communicate. On my own initiative, I flew out to where the rest of the project is located. It was for 2 days, and it was extremely productive - indeed, essential.
There always seems to be a mandate in organizations that people travel too much, and it needs to be cut back. I look at it the opposite - people don't travel enough.