The coffee table and end tables do not have to match in color or shape. In fact, it is often a good thing to have a mix of square and round shapes in a space.

With all the grey that you have, sticking with wood for the end and coffee tables is a good idea. If you have children, and/or children visiting, a round or oval shape on the coffee table is even more beneficial. No sharp corners. Or even better- an ottoman style coffee table- in a leather or faux leather could work. Using an ottoman style is the best option with children; and it is also a nice style option, in general.

ETA:

I created a few visuals. Have not seen any pics of your space, so can only guess at the furnishings, etc.; these are just general ideas/views.

I agree with freedomplace1 - the different pieces don't all have to be the same but I will say it is generally good that the pieces relate to each other thru color and general style.