This was our 15th cruise on Celebrity. In 2011 we took our eldest son with us (who was 8 months at the time) and had a great time on Eclipse. Previously we had just cruised as a couple.
So ... based on previous experience we booked a 2 week cruise on Eclipse with my parents and our two sons (aged 1 and 2 1/2).
We booked a family room which was amazing - 2 bedrooms and a huge lounge/dining room. There are only 4 of these cabins on the ship and they are one of the best kept secrets - the square footage was similar to the Royal Suite. The only negative was that there was no bath - we improvised with a paddling pool for the children!