This was our first cruise and one which we were nervous about as a young family as much was unknown. Our fears were allayed as soon as we walked on the boat to great service and lots of activity.
The constellation is certainly not the ideal cruiser for an 18 month old child as all services are for children 3 and older (although you could use baby sitting) and as such you will spend all your time with your child (which was fine for us but not if you want a break)
The destinations were superb and the precise reason we went, stockholm, warnemundew, amsterdam, tallinn, st petersburg and copenhagen were all great. Helsinki was a bit of a let down with very little to do or see although the shopping was good. £6 for a pint of carlsberg in copenhagen was a stretch (especially as I buy if for under 70p to sell in my business's)