i would set up the tank like this:
get clean, rinsed gravel and put a half inch down
make a raised land area ramp on one half (start the ramp halfway so a third of it is above water)
the top of the land area should be about 4 inches
spring or dechlorinated water ONLY!! fill until you come close to 4 inches of water
cover the exposed land area gravel with some moss (NO ECO EARTH!)
dont worry abt exposed water gravel, they wont accidentally swallow it if it's underwater
put a small fake cave on land and in water float and insert plants into gravel, real or fake depending on budget
lamp over land with 40 watt bulb and u r good to go!!
make sure to siphon the water/gravel (swirling it and collecting the junk with a betta net works well, no filter needed, weekly water cleanings needed and every 3-4 months take apart everything and rinse it
also, if the kid holds the frog, be sure they wash their hands afterward