Thank you for starting this new interesting project.
I think Ubuntu is the best Linux distro at the moment, offering a better hardware support, an huge repository of packages and a nice UI.
I am a C++/Java/PHP developer and i use very cpu-intensive tasks and i would prefer a fast CPU, but, for Web and Mobile development, a middle-level CPU as Core i5 is enough. By the way, a good improvement is the usage of a SSD drive, in order to boot up and to resume/hibernate the notebook in some seconds, keeping the battery life high and obtaining a very responsive system. The RAM quantity of 4GB are enough too, since Linux doesn't eat RAM like OS X or Windows do.
Of course, graphic card power is important, if you plan to write 3D application: the best solution would be a nVidia Optimus system, but for that, Linux isn't still ready, because the drivers for this operating system are bad.
For tools, i would prefer the Geany editor, ccmake, Android SDK and some free RAD framework, such as CakePHP or CodeIgniter.