One option is lining up with him in the preferred corral. They'll let you move back a corral if you want. If you don't want to do that, they drop the divider right before the start, if you line up in the back of the competitive corral and your partner can work his way to the front of the other, you'll be able to meet within the first mile. Just make sure you make eye contact before the start so you know where each other are.
A cautionary note: Beware of jackasses sprinting and pushing from behind. That's the only problem on what is otherwise a really organized starting area.You see them every year pushing their way by people the first mile, then you see them again at mile 21, hanging over the fence by the Dan Ryan expressway with "cramps".