I would suggest getting a stripper but..u said acceptable..so..

Get a TONNE of booze (you wanna make sure the guy turning 21st is the drunk-est on the floor).

Party party party. If there's snow outside, birthday boy lai jhanakutti parera hiu ma faldeu.

Make sure you have a DJ who understands his drunk crowd. Its really easy to make em dance when they're drunk. Play songs that EVERYONE knows. Hip Hop is usually alrite, but I try to throw some cheesy classics in there as well. Like Peter Andre - Mysterious girl, or Whigfield - Sexy eyes. You know the ones u used to secretly listen to while in 8th grade.

If you want, cook food, but if ure the lazy types, order Papa Johns.

You could enforce a costume rule but, being Nepalis, I doubt how many would actually obey. Just make it like everyone HAS to wear half pants or smth silly. Its going to be memorable :D. Half pants in the snow would be torture tho..:)

At 11:50, make the birthday guy give a speech and get it recorded for future viewing. (just don't put it up on FB :P)

Ani after the party when everyone is drunk and tired you can play truth and dare, or spin the bottle :D

These suggestions are for house party. If you are going outside, id say hit a bar or a club :) but thats overrated :D

Cheers, and happy birthday.