How about London Grill (in the Benson)
The London Grill is a rather humorous experience. One could have an entire 4 course meal done flambe'! Of particular interest was the foie gras in beef gravy (flambe'). The ostrich I had there was excellent. There are better restaurants for sure but if it's prom night, it should be on the top of your list.
London Grill is an old-school french-inspired restaurant that would be perfect to take your parents or grandparents to. Steak's on the menu, but it's not a steakhouse. You'll love El Gaucho for steak. If you want to avoid drama, skip the caesar or the spanish coffee.
However, if the gadflies on Chowhound still have you worried, you can get a great steak at Higgins (about 1/3 mile n. on Broadway), or the Heathman (even closer on Broadway) or even the Portland Steak and Chophouse in the Embassy Suites. This would be my recommendations from most recommended to least. If impeccable incredients is your top concern, go to Higgins. For the best steak, I'd really stay with El Gaucho and keep it simple.