Alcohol and barbecues on a 1200cal diet

It's your home, you can eat and drink what you like. Also, for future events, since it's too late now, you can plan ahead and eat a lighter breakfast and lunch to save calories for dinner. But, I wouldn't recommend skipping a meal lest you become ravenous and eat everything in sight at the bbq. In the end I just wouldn't worry and just plan on getting back on track tomorrow. One day isn't going destroy all your hard work. Have fun.