I'd try to help them out, in some form. I honestly don't expect to get married, much less have children, but if I did I probably would not seriously try to dissuade them from such a course. I would try to influence them towards having "many options", but I would not be seriously upset if they chose that course.
Then again... I don't really know. I don't think i'll ever find out either.
Seriously? It's their choice, they're old enough to enlist they're old enough to know what they're doing, so I'd support them. Not that I have any intention of spawning broodlings in the near future, although I would be pretty happy.
"Cut the grass"
"Now wash my car"
"What are you complaining about? This is going to seem like paradise compared to basic, so get moving"
*small aside before someone tries to chew my asterisk: Three of my uncles were combat engineers and one was an infantryman who became a career officer, so I respect the uniform and the people who have worn them. I just don't respect some of the reasons people are putting on the uniform for these days.
I would say "Ah hell no, you're joining the resistance now grab all your ammo and sturples MRE's were going into the woods to ramble on about goverment conspiracies and potinal zombie attacks!Prolly cause by the goverment!!" Then my kid would say "Okay Dad, well I'll be going now you stay here with the nice people, okay?"
OT: In reality i'll have driving my hypothetical kid into the loney bin.
OT(for real): I would be proud that he has something to aspire too, inless of course his just doing as a last ditch effort. I would also explain to him that there is no good in joining the military if all you want to do is "See some Action" because if that the only reason I would pop him on the head and force him to get a office job for being so stupid.
I be worried for their saftey, war is a dangerous thing after all. I wouldn't want my kids preforming atrocities upon others, nor experiance such things, I also wouldn't want to lose them in a pointless war that just benifits the rich and lowers the population of the poor. So in short I'd be scared for their safety and their innocence. And if it was comparable to the Vietnam war I'd probably soil myself.
I would be proud of my child/children for joining the service. It's a HUGE life decision that would require much thought and consideration. It is also a great way to start a career, and it looks absolutely AMAZING on a resume.
If my child (who wouldn't be a child if they joined the Army, Marines, Air Force, or Navy) wanted to serve, then I would support their decision. However, that is not to say I wouldn't be worried about them the whole time.
As a peace loving hippie, I'd be pretty damn disappointed that my children, the ones I've raised and taught since they were tiny, would go to war and kill. But in the end, regardless of how I feel, it would be their decision, not mine, and I would respect every choice they would make.