Sounds like you have a plan then.
I'm impressedjust a few days ago "what's this EAGLE then?"today "I've ordered the boards"well done you!
Ok, now the tricky bit - draw a polygon (button looks like a piece of paper with top left corner torn off - click a corner follow the perimiter of the board, must finish up where started or will get "illegal poygon" error or similar), name it GND, on both sides of the board. Your thru holes will connect them. Click the Rubberband button, and let eagle connect everything up to GND. May even be to "ripup" the ground traces.