My fiancé and I are hosting 4 hours of open bar for our guests (1 hour cocktail and 3 hours reception) however, our friends are pretty wild and will most likely not be ready to leave the party at 10pm when it is scheduled to end. The hotel we are having the reception at has the room reserved for us for the entire night at no additional cost and we found a DJ that is reasonably priced for additional hours of music. My question is, if we want to keep the party going after the 4 hours of open bar are up, is it tacky/inappropriate to change the bar from open bar to cash bar and ask guests to pay for their drinks for the rest of the night?