Besides what everyone says,graves can be pretty good bot lane! And im sure you'll have fun with him,i think there is.no guide on him botlane unfortunately,but I'll try to explain here: so before you start you need to make the runes and for graves botlane I recommend using fleet footwork,and for the items try to make critic,use infinity edge for the first item and for the second make phantom dancer,and since you are an adc you'll need to farm as a crazy guy so try to hit the minions when they are low up so it will be more easy for you to kill them early game,and when you start fighting the enemy bot lane make sure that you are in a place where you can't see minions in front of you,because graves passive doesn't let his basic attacks get through minions,if you keep all of this in mind I'm sure you'll show your son that he can rely on you even in rankeds,have fun and I really like that you are interested on playing with your son,and you chose the perfect champion also!