Legal Question in Family Law in Texas

Yes, he can (and obviously did) issue a citation. As to whether or not it would hold up in court, it doesn't sound like it. Proving up a Class C assault means producing evidence that the defendant:

1) intentionally or knowingly threatened another with imminent bodily injury, including the person's spouse; or

2) intentionally or knowingly caused physical contact with another when the person knew or should reasonably have believed that the other would regard the contact as offensive or provocative.

While with a more serious assault, it's at least arguable that the State may not have to produce the victim as a witness (if others can testify as to injuries, bring photos, etc.), it's actually pretty hard to do that with a Class C. What one person finds "offensive or provocative" is obviously not going to be what others might find offensive or provocative. If I went up to some random stranger at Target and hugged them, they'd probably be at best a little weirded out. If I saw my best friend in Target and hugged her, it'd be just another day. So I don't see how they can make a case without getting the other kid to testify, unless this was actually something where someone heard your son say "I'm gonna kick your ass" or something? Regardless, if it really all was a misunderstanding, I imagine that a call from the other kid's parents to the person handling the case might be helpful.