shouldn't be too hard.  The military wants its members to pay their financial obgliations. The military is more than happy to "assist" its members paying their financial debts. (read garnish wages)

(I think)  If you contact the Military, show copies of all your paperwork, proof of responsibility, non payment etc.. they will "adjust" his behavior accordingly.

$25/month ??  that is crazy, he is 1/2 the responsible party, he gets to pay his half of the responsibility. He should be paying something around $400-$500/month.

Child support Enforcement hires all their people from retired IRS or the loan shark industry.

Avoid just going out and hiring an Attorney,, the sharks will want 1/2 of what should rightfully be going to your grandchild.

Here:

http://www.wikihow.com/Collect-Child-Support-when-Everything-else-Fails

http://www.acf.hhs.gov/programs/cse/fct/fct2.htm

http://family-law.lawyers.com/child-support/Divorce-Paying-and-Collecting-Child-Support-FAQ.html

This is where you send the Court ordered paperwork to.

http://www.child-support-collections.com/military-child-support.html#1   

Forms to get you started, and/or what forms to ask for at your courthouse.

http://www.uslegalforms.com/prodpages/US-01600C.htm%7Cfdlaw