What do you think? --can I recommend dice and roulette gambling game since among the poll I listed this is the easiest gambling I have ever known. I added a poll and lock this thread once I have got satisfied answers from our fellow gamblers on this community.
Safest? None of course.
Instead, explain to them the risks of doing gambling and what are the factors involved in playing a gambling-game that faces the house e.g dice, roulettes and slots.
These games might be easier to follow and understand but in terms of winning probability, you are actually relying on luck alone if those random hashes will hit your desired pick or bet each roll.