Welcome to RCU.
So you need more info on some things. After you order the LiPo batteries and charger(s) I would look at/familiarize yourself (and kids) how to properly use the chargers with LiPo packs...
http://www.rcuniverse.com/forum/rc-car-general-discussions-179/9346308-rc-resources-beginner-read-first.html
I am sure someone will jump in here with some help...I gotta go to work. In the meantime, check out
SMC and
SPC Racing Batteries.
They have been a favorite be many over the years.