Which technology stack to use for car pooling over web and mobile

I want to start working on a project where I want to build a intranet website and mobile app for people working in my office for car pooling. The basic idea is that if anyone is interested in looking for someone to carpool with should make a posting of going from A to B at time X.People can then reply to it.

I've narrowed down my option to Scala+Lift+MongoDB or Node.JS+Redis/MongoDB+HTML5. I don't know which one is better or worse for the problem I have mentioned. Also looking at developing mobile apps for the same application where people can send carpool request over their phones.Looking for a stack which can complement the mobile development also.

I know there are various solutions for this, but I'm looking to learn something new and exciting and have fun while developing it.