We did this same cruise in 2023. It was our first “big ship” in the P&O fleet. Since then we have been on Iona twice and the Arvia TA was certainly the least busy. In the interests of clarity I should say that we don’t eat much in the buffet or MDR and these are generally when you would notice the crowds. There were a lot of young families on our recent Iona cruise, many with under 5s so school holidays were not an issue. Being realistic, if you choose a ship with that capacity you are looking at a busy cruise.