Using skimpy glass sizes not only gives the appearance of being cheap, but it also increases the traffic at the beverage service areas which increases congestion at the bar and glassware and ice usage.
12 ounce glasses are recommended for mixed drinks, beer and soft drinks no matter what the type of event since it gives the guest a reasonable portion and allows you to more efficiently utilize service personnel by decreasing the number of times a guest will return for a refill. On the other hand, using a glass size larger than 12 ounces, especially in warm weather, will create waste since the ice will melt or the product will warm before it is consumed which adds to wasted glassware and product usage.
Wine should be served in 6 ounce glasses with a 4.5 to 5 ounce portion for the same reasons.
For large picnics and grand opening events, beverage carriers are a nice gesture BUT they increase waste since people tend to take extra which ends up as waste due to warmed product. Allowing attendees the ease of obtaining a large number of beverages at one shot also decreases the amount of control you have when it comes to excessive consumption.