I doubt it would take you long to learn PHP/HTML/JavaScript since you already have programming experience. I say allocate a certain amount of time to learn/code. Try to get a decent version 0.x in that amount of time. If you then find that you still need to outsource at least you'll be in a better position to manage things.
Markus Frind learned ASP.NET while using it to build the successful dating site PlentyOfFish.com (he too was already an accomplished programmer).
Markus Frind learned ASP.NET while using it to build the successful dating site PlentyOfFish.com (he too was already an accomplished programmer).