In previous years, I used a backup battery bank, and it worked well enough, but it was pretty bulky in the pocket, I had to remember to charge it every night, and if everyone needed a recharge during the day, it would run out of power on us.
This past summer, I bought one of the fuel rods while we were at Disney, and absolutely loved it. The value in the fuel rod is in the ability to instantly exchange it for a fully charged replacement at any time in the park. We were able to keep phones charged for a family of 5 with just one fuel rod! As long as they continue to have the kiosks in the parks, this is a great investment.