We just got back a few weeks ago from an NCL Greece/Turkey cruise on the Jade. We could have got a comparable VGT rate with
DCL but I specifically wanted to see Knossos on Crete (not feasible with DCL since they port on the other side of the island).
With DCL the ships are part of the attraction for me and I spend a lot of time trying to take it all in. I didn't feel the need to do that on the NCL Jade. So in a way, it was a better choice for this trip since the time I did spend on board was more relaxing. I agree with ljhayes that it was more like a floating hotel instead of an experience in itself.
Not sure what your family's interests are but we didn't have much interest in the entertainment options (only saw "Elements" which was glitzy-Vegas-y). I spent most evenings after dinner in the Thermal spa (Rainforest room equivalent) and only saw 4 other people in there during the entire cruise, so that's a good chill option.
We thought the food was mediocre and the main dining room menus were a bit repetitive as the week went on. We had a "Free at Sea" package that included 2 specialty restaurants so we tried Le Bistro which was a step up, and Moderno, which was not. The buffets had a lot of choices but it's your basic buffet food. They did have an Asian food station but the only inclusion of local cuisine was a "Greek Night" once on the buffet.
The Jade seemed to be in decent shape. The only thing I noticed were some chairs in the Alazar restaurant where the vinyl was chipping off.
Staff was cordial and efficient (sometimes a bit TOO efficient, not waiting until the posted closing times to clear the buffet, pool loungers, etc).
Embarkation, muster drill, debarkation were all quick and easy. We did have trouble loading our required pictures on the website prior to the trip but they were able to take them at the port. It was a nice bonus that the port departure times were no earlier than 6pm, and at Mykonos and Santorini, 9pm. That gave us enough time to do both archeological sites and hit a beach at most ports.
Overall, while the NCL Jade doesn't compare style-wise to the DCL ships, it was perfectly adequate for what we needed out of this particular trip. I wouldn't hesitate to use NCL again if I had a similar situation where I needed to fit a specific itinerary.