You should take into consideration that the mini is not that powerful. You can either have a dual chip with mediocre/tolerable graphics (may or may not be important to you) or you can have the server model with a quad laptop cpu and discrete graphics. Overall you could have a more powerful machine buying a refurb 2011 pro than the mini for less money spent overall. The Air has been updated this year. Geekbench isn't a perfect reference, but 64 bit geekbench quad/server mini = 9448 and i7 air says 7575 (weird number, I wonder about that). The 13" pro is listed at 8585 or 7717 for the cheaper one. Unless refurb pricing or third party retailers offer a better deal on the mini, this basically makes that a waste of money for your purposes. The 13" pro isn't even remotely heavy. I'm not sure how the HD4000 compares to the discrete mini, but the HD4000 is clocked higher in the 13" pro than the Air.
I'm trying to say that going for 2 machines here is going to cost you more for very little benefit if you're buying today. Also not everyone knows that the HD4000 is clocked differently between the two machines. In case anyone is going to mention the HDD vs SSD point, the mini would have an HDD by default.
Edit: I'm not saying the 13" pro is an amazing gaming system either. I'm merely saying that the others look pointless to me here. If you're trying to save money a refurb 2011 15" is not a bad deal at current pricing, and most of them have better graphics cards than any option in the mini paired with a quad cpu. Keep in mind ANY of these machines listed will get very hot while gaming.