I say that you should get it because it's something that you obviously don't plan on hiding from your kids, and it would be better that way. If you are honest and open with them about it and expalin to them that you think that it will be okay to do it when they are older than they will hopefully respect that. But samwhore is right they will most likely smoke during there teenage years. But if what you are worried about is them wanting to smoke at a young age and using your pot leaf tattoo as an excuse for them to do it, you can just remind them that you think its okay if they toke up when they are older.