If you decide to go with Unity it's relatively easy to setup most of the coding. Here's an example project http://unity3d.com/support/resources/tutorials/2d-gameplay-tutorial
Check this out : http://udn.epicgames.com/Three/CameraTechnicalGuide.html#Example%20Side-Scrolling%20Camera UDN in general is a great resource if you're using UDK, don't forget to use it.