Personally I would stay away from fingerprint readers. Wet hands, even from sweat, can interfere with them and cause failures to read properly. Your print can also be pulled from the display fairly easily so depending on the age and curiosity of your kids they could still access it.
I agree. Not a huge fan of fingerprint safes. I have a quick access sentry safe (
http://www.sentrysafe.com/HDC/Quick_Access_Pistol_Safe) and have had no problems. You can custom program your own code. Very simple and easy to open. Cost $99.