If Congress buys into the idea that fighting with terrorists, specifically terrorists who have ties to the same insurgents we're fighting against in Iraq is a good idea then they should be willing to take that gamble themselves. They should all enlist in the military, put on their uniforms, and fight for our country, or rather our president's misguided foreign policy agenda.
Since they aren't going to do that they can all expect less votes when they run for reelection.
Few congressmen would pass the rigors of boot camp, nor should they get the 9+ week vacation from the important job of running this country. However taking their first born children (or grandchild depending on the age spread) would make more sense.
There are probably a few eunuchs in congress who would be immune, but likely not enough to be a decisive factor. There are also of course those who desire the death of their children, but at least it'd be fair (fair assuming a war got bad enough to reinstate the draft).
Sending Congress to fight in any war it approves of is not something that I can agree with. First, it gives Congress a vested interest in ignoring logical arguments for and against war (which is not good; war should be rejected for reasons that stem from rational arguments, not selfish desire for self-preservation). Furthermore, if Congress leaves to fight, you're leaving the task of governing the United States to... Whom? Although it is popular to say Congress never gets anything done, it is one of the three branches of government and is immensely important to the governing of the country.