You are correct that they should have been more prepared. I am not a 4-wheeler so not familiar with the Rubicon trail so cannot comment on its risk. I doubt they knew what they were getting into. Not an excuse for not doing their homework, but I would not extrapolate that they intended to put their infant at risk. Stupid mistake but I hesitate to call it intentional neglect. They definitely got in over their heads. If I were to speculate, I would guess the mother simply trusted her husband to handle details and assumed they were going on a few hour fair weather jaunt. I regularly see wives or girlfriends blindly following while backpacking with husbands or boyfriends. May not be all that different in the 4-wheeler world. Bet the guy is in the dog house now!