In my expierence, C++ programs have compiled faster than C, i dont know why (maybe its the C runtime or something). So speeds really shouldnt make a difference there. So C++ would probably be a better choice than C simply because it Object Oriented things like Classes. You dont need to understand them to use C++ (in fact, a C program will compile under a C++ compiler in almost all cases).
As for graphic engines, SDL is a good choices if your going to do pure 2D games, but past that I would suggest DirectX (I assume youre using windows). DirectX is pretty standard among game developers, and it has things like built in .X file loading so you dont have to code that yourself. Very good system.
Hope that helps, teh ionman.