If you get those little plastic tanks for reptiles. Umm, like 4 gallons or something, that should be enough for a betta and they also sale lights that fit into the feeding hole in the top. the light should actually provide some heat for the tank as well as keep it bright. also like someone mentioned they have mats you tape under the tank and plug in. I honestly think this is your best bet for kids. i have used this setup and know it works. my only wory with heaters in the tank is that it could potentially get too hot and kill the betta. speaking from experience though the small plastic tanks sene here and the heater for underneath here . i have used that equipment for a long time and it works well. right now it is no longer a fish tank but a hermit crab cage for someon else. but still works