One expedient used by less affluent pipe bands (or bands in hot places) is not to wear a jacket. Use a long sleeved white dress shirt and wear a black waistcoat (vest). You may well find a good one at a thrift store, actually.

As to tie, the rule I like to use is that black never lets you down. Black vest, black tie, white shirt and you will look sharp. Cream hose will almost certainly work fine with the ensemble. However, would just a vest be too informal for this event?

My wife's rule of thumb is that if something looks appropriate for the occasion from the waist up, it will generally be acceptable with the kilt. So, for example, while lots of people love poofy "Jacobite" shirts, if such is not appropriate for the chosen venue when worn with trousers, it will not likely be appropriate with a kilt.

I'm going to say that some sport coats are cut lower than others. Try yours in front of a mirror and see what you think. I suspect that it will be too long, as others here are saying, but it is worth trying it on. If in doubt, have someone take a picture and post it here for advice.

There is also a thread with lots of discussion about formal wear with the kilt on the cheap. I seem to recall the idea of a waiter's tux jacket being easily made to work well. The cost was in the neighborhood of $30 for the jacket. Look for that thread for details.

-Patrick