QF can be reheated and cooled as many times as you need without compromising its effectiveness. Sunlight has adverse effects with QF, so keep it out of the sun.

The best thing you can do in this situation is practice. Get a childs temp strip (or digital thermometer) and record the temperature. Heat it to 100 degrees and place it where you'll be carrying it. See how long it takes to dip below the desired temp. Attach a heat pad and see how hot it makes it and how long it takes to get there..

If you practice practice practice, you'll know what you have to do.