And I somewhat disagree with Dan. I do love HAL, but I love NCL also. They are totally different experiences. we found the food in the sur charge restaurants outstanding and the portions very acceptable. In the main dining rooms I do agree: the portions are small. To me this is better than wasting food. You can alsways ask for more. We also enjoy the variety of restaurants and found the specialty dining rooms better than Pennicle Grill considering the price.
The cabins on HAL are larger but we like the overall energy on NCL and the entertainment they offer. The service is a matter of opinion.
If your sister likes freestyle, you are unsure of NCL and your wife's partents really are not crazy over NCL have you thought about Princess? They have Personal Choice dining which is similar to freestyle and offer great food. I think their entrees are outstanding, but HAL has better buffets. Of course I think a buffet is a buffet. You have only part of the freestyle idea right, but it sounds as though you have made up your mind not to enjoy what NCL offers. This being the case it may not be the right cruise line for you.
Even though we had some mixed feelings after our Princess cruise last month it does seem this would be a compromise for you.