Nicolas, sorry for the delay, I was away. You're very welcome.
I used some DC power connectors, barrel-style. I got them from Amazon and there were 10 male, 10 female (both with pigtails), and 10 male and 10 female with screw terminals. When you say "banana connectors" I think of the style of connector commonly used on multimeters. I've had some really shoddy ones on a cheap, Chinese multimeter many years in the past...I'm not a huge fan. I cannot say definitively whether you should or should not use them, but I can say I would look at them very carefully. The ones I encountered and hated had slits in the male pin like a + sign and the only "springiness" was minimal. The "springiness" was not really good at making constant connection and the pins seemed fragile in terms of being able to bend the 4 petals ever so slightly, reducing their contact with the female port. I'm not describing it well so I'll say this: they were sketchy. Regular screw terminal blocks might be a good choice, too.
Be sure to check the datasheet on the 7805 for input and output capacitors. Also, bulk capacitance may be beneficial to add but I cannot say how much because I don't know enough...I'm new, too. 
Have you implemented anything to handle the back EMF/spike from the motor when it is turned off?
--HC