Are any of his kids old enough to legally OC around the house? Might as well give the CPS government agent something to wet his/her panties over.
All kidding aside, I'd definitely require the CPS agent to jump through all the legal hoops forward and backward over such an unwarranted intrusion into theit private lives, but that is just me! There is nothing good that can happen over cooperating in my humble opinion. Just make sure he sets his mind to going the distance with these folks, encourage him not to give up his rights. Good luck!
If dealing with CPS on his own property, I don't see any reason why he couldn't OC. Don't foget to advise him to cover hishiney with several video and audio recorders. Having some witnesses present wouldn't hurt either.