Full board cruise, inc tips...based on 2 sharing.
You have various options here!
£340pp is for an inside cabin. A Balcony cabin is £450pp which you may wish to consider.
The all inclusive option (incl drinks up to $16 value) is also good value at about £28/29 per day by my calculation.
In addition, children under 11 are only an extra £99pp... Therefore 2 adults and 2 kids sharing a cabin would be £212pp...see below