You can't realistically consider Matthew 18:8-9 without starting with Verse 6:
6 “If anyone causes one of these little ones—those who believe in me—to stumble, it would be better for them to have a large millstone hung around their neck and to be drowned in the depths of the sea. 7 Woe to the world because of the things that cause people to stumble! Such things must come, but woe to the person through whom they come! 8 If your hand or your foot causes you to stumble, cut it off and throw it away. It is better for you to enter life maimed or crippled than to have two hands or two feet and be thrown into eternal fire. 9 And if your eye causes you to stumble, gouge it out and throw it away. It is better for you to enter life with one eye than to have two eyes and be thrown into the fire of hell.
Did Jesus mean 8 and 9 literally? Of course not. It was his way to teach via parable, allegory, metaphor, symbolism, but the point made is clear:
If what you are doing will result in hell, don't do it. Most especially when you do things that harm others, most especially the children.