I have not finished reading the book, and in fact am only a few chapters in but am enjoying it. I saw the movie, and really liked it. On the question of "why didn't they just take them along until the pickup came?" I would just be throwing out a guess here but perhaps they were so confident of their communication technology working that they didn't think it was something they needed to consider doing?
Also, they obviously didn't think the other team could move so quickly in that terrain. Since it's based on a real live event, they obviously did what they did and had to face the consequences of the decisions that were made. But technology sure can fail you sometimes when you need it most.