The "anime we disagree on" panel sounds interesting, but it sounds like the kind of panel that would need to be moderated so that things don't get out of hand. After all, it only takes one "because" to set someone off (in certain cases). Also, it could use a catchier name (though I imagine you've thought of that already).
If I could offer a suggestion, change the "otaku" from your "I like" game to "nerd." Given the negative connotation that otaku has, it'd be a good idea to try to bring it back around to a term that no longer has as much of a negative connotation. You'll also want to watch out for people intentionally singling out other cosplayers (within reason).
For the King game, you'll need to figure out both how many people participate in each round and how many numbers can be ordered to do things. For example, will you only have 7 people play at a time, cycling out each group after they've finished playing, or will you plan on having upwards of 50 people (assuming there are that many participants) per round? And will it be one or two numbers that can be ordered, or upwards of 10 (assuming there are that many people)? Finally, you'll want to make sure the orders are within con rules (whether it's an all-ages panel or an 18+ panel, rules are rules) and determine whether the king can participate in the orders. (For example, can the king order #5 to give the king a back massage, or would they only be allowed to order #5 to give a back massage to one of the other numbers?)