Tom,
We are going next July...on the Celebrity Constellation...
I've cruised on six different lines...I've cruised Europe on both Princess and Celebrity...
...and in my book, it's a no contest...
The Celebrity M-Class ships are simply outstanding...and the service and food are superior...
And comparing itineraries between the various lines, Celebrity tends to have the best itineraries...
Our sailing (July 16, 2005, 14 nights) does this route: Dover--Le Havre--At Sea--Cork--Dublin--Belfast-- Glasgow --At Sea--Olden--Geiranger-- Bergen-- Copenhagen (overnight)-- At Sea-- Dover...
No Northern Europe route is great for the kids...simply not as many as they'd find in the Caribbean or Mexican Riviera...But, my kids were absolutely lonely on Princess in the Baltic...the average passenger age seemed to be about 85...I'd guess (based on my experience with Celebrity in the Mediterranean and Alaska), it should be a little better...
But,again, the main advantages are the service and food...and style...
Good luck...