While these don't have listings in NM, the following two articles on GORP.com (an Away Network site) profile some awesome rivers that might suit your family: http://gorp.away.com/gorp/activity/paddling/top10_kidrivers.htm, http://gorp.away.com/gorp/activity/paddling/top10_kidrivers.htm. Hopefully of some use as you're planning your trip. Also, as you're in Texas, have you considered Big Bend NP? Some great floats there, or you could try the Texas Gulf Coast. More ideas on that front at: http://gorp.away.com/gorp/activity/paddling/pad_tx.htm.