The best thing you can do as a leader is to stay out of other people's way.

Your job as lead is to maintain an overall "big picture" view of the project, while being able to drop down to any level. The best leads I've seen are always available to help, always try to be involved, but don't step on their team member's toes. Some ways to achieve this:

 - Expect team members to make decisions about the implementation of their area. This should help them to take pride in their work, which will make the project better.
 - Be aware of what is happening on the project at all times. This means **communication**. You could have a scrum-type daily meeting, or just chat with the individuals every now and then; whatever works for you and your team.
 - Don't micromanage — once you've handed off a project facet, let the person assigned handle it unless they need your help. But don't force help on them. I had a team leader who was the most approachable person I've ever known. He somehow made it plain that he would always help, without forcing himself on us. Not sure how he did it, though.

I wouldn't worry too much about the choice of languages. You can learn any language you need to; experience on other projects (even in other languages) will only help you. Just remember that's it's more likely that your team knows the language better than you, and be prepared to defer if necessary. You will have to work hard to bring your own skills up to par.