Cheating

During the prerelease I was cheated against.

One of our group of EDH players is known to misunderstand the rules. He brings his kids who are also very bad about it.

During the prerelease tournament he and his kid both tried to cheat against me. Some of it may have been an accident but the guy definitely did one thing on purpose. Our tables were too big and it was impossible to read each others cards without standing up or handing them to each other.

The "accidental" cheating was mana color and number manipulation. They both tried to tap all their mana at once and then play 2-3 spells at once. The problem being they didn't have enough mana or the right colors. Every time I pointed this out they fixed it.

During the second game against the adult he plays the green land that allows you to sacrifice it to create a pilot. It enters tapped. He immediately sacrifices it. I said "don't you need to tap that to do that?" He says that he is tapping other mana for it... I said sure but the cost includes tapping that special land... He reads it and says that it doesn't.

At this point I am pretty sure he cheated but I don't want to make a scene by calling the judge on this guy. I later looked up the card to verify his cheating. I ended up beating him because he isn't a very good player, but I can't help but think that he cheats like that a lot in EDH as well.

Should I have called a judge? Do you think he deserved a dq, or can this still be chalked up to him misunderstanding it?