There's no right answer here. You can certainly do fairly well with a WCF RESTful service. Or you could use ASP.NET MVC. Both are perfectly valid, and both have strengths and weaknesses.
Ultimately, I'd suggest you go with whatever feels the most maintainable to you.
I would like to note that MVC 4 is in beta, so watch out for bugs and don't go live until it's out of beta.
