How to cross the river hmmm you could just avoid megs while going through its what i did. If there is a lot of megs then depending on your and your sisters level equipment raptors lvl and megs lvl if you your sister and raptors are good I would just kill megs and bring sarco to help if your not good then I really don't know I haven't dealt with megs much but I did kill two when I was alone in hide armor with nowhere to go. But thats me not you.