I plan to take my kids on an overnight hiking trip on the AT near Lynchburg VA. We plan to go in late April or early May, so lows should be in the 40s. I have ENO hammocks and 20* bags for them. My question is will a folding or roll up foam sleeping mat be good enough insulation for them? I'm not sure how many of these trips we will make so I don't want to break the bank for only 1 to 2 trips a year. Thanks in advance for all the input!