Well the good news is that you trust the capabilites of the people working on the project. That makes it significantly easier. You know project management, so you know how to keep them on track as far as budget and deadlines, etc. When they want to do something you don't understand, ask questions. You want to feel more up to speed on the subject, so make sure you aren't questioning their judgement but rather trying to educate yourself.
Where the biggest problem comes in is when you need to make a choice when two (or more) of these people disagree about what to do. In this case, I recommend that you have them do a formal decision analysis where each rates what they want to do against the criteria that you determine (hours to develop, performance, etc.) Then once you have those ratings, go take a quick look around the Internet to see if they are relatively correct. Once you have a rating for each choice for each possible criteria (and you determine the relative importance of the criteria based on project needs) then it is usually easily to see which is the better choice. Have them bring their analysis to a meeting and discuss so each side has a chance to shoot holes in the other's argument. But make them keep it civil.
Weighting Plan A Plan B
Criteria factor Score Total Score Total
Performance 4 3 12 4 16
Maintainability 3 3 9 4 12
Development Speed 3 2 6 2 6
Security 5 5 25 1 5
Total 52 39
After you know the people better, you will have a feel for who is usually right, then you may give some extra credence to what that person wants to do, but remember, no one is right all the time and automatically picking George's solution over Simon's every time will make Simon resentful. So truly listen to both and choose based on the criteria you give them.