I guess my concerns have already been voiced over & over, fact is you-all will have parties, fact is they can get violent (been there done that bought a t-shirt).
Personally, I don't like the idea of non lethal rounds in a weapon, for instance, if your first 3 rounds are non-lethal, you've got quite a few seconds prior to cycling to the lethal rounds, those seconds can be VERY important.
I also don't like the idea of a shotgun @ a party setting, shotguns are used by law enforcement in a setting where pretty much everyone is a bad guy (typically used as an entry weapon into a house full of bad guys). Your party really doesn't qualify as a houseful of bad guys (hopefully).
I do like the Taser idea, and I like Air Taser's better (the ones that fire electrodes on a 15 foot or so long wire & catch the bad guy's clothing), if you do go with the Taser, check your local ordanances to see if there are any regulations on Tasers where you'll be living.
Every time I've used a weapon, (and I've spent a night in jail after using a weapon to defend myself-charges dropped after the bad guys were sorted out, it was funny, the DA ran all of us through the computers-my rap sheet had my name & 1 traffic stop, the other guys had 4+ pages of priors). It turns out the police get real upset if you haven't @ least tried to call them about a situation where you feel deadly force is necessary and you have time to call 911. Be warned, every time you pull out that shotgun, even if you're in the right, you have the very real possibility of having to look the DA/Judge in the face and explain every aspect of the incident, and that you'll be judged by what a "Reasonable Person" would do in the same situation...