Actually, the PIC16F690 is better. I has more I/O pins, more memory, it has an A/D (so you can use the pot), two comparators and it has a communication interface (which can be used in the future to connect serially to a computer for example, or to easily connect other devices to it). It can definitely make future projects easier.
Plus, this eval board can be saved to use as a programmer for future projects, using 8, 14 or 20-pin PIC's. The price is right, too.
Therefore, I would just go with the PIC16F690, even though it seems a bit of a waste, seeing that you will not use it at its full potential. Perhaps a better choice would be a PIC16F505, which can also be programmed with pickit 2.
The only reason I recommended the PIC16F84 is that it is a very popular micro and easily available.
I will update the schematic, but it may take a while, since I am really busy this week.
Can you give me an idea of the motor currents?
Do you have already any relays to control them? Which type? This is important to correctly select the transistors.