I don't where else to ask this question and I think this is the best place so I'll ask here.

I'm making a remote controlled boat that uses two DC motor controlled by a L293D motor driver chip. It takes power for driving the motors from 4.5 volts to 36 volts. To supply this, I'm planning on using two 9 volt batteries in parallel. Would this be fine, or is there a better option like 4 aa batteries in a series? I don't know much about batteries and the like, so there might be something that would make this not a good idea that I don't know about, so that's why I'm asking here. Thanks.