Spain Easter Week

Depends on where within the country you’ll actually be, but as a generic statement, any town or city where there are processions will be busy. Cities like Sevilla will be insane. Hotel costs also skyrocket during that period. If the cruise has a tour to see any of the processions that makes it easier on you.

Though I understand trying to avoid peak travel time, think about whether you will ever have the opportunity to see these processions elsewhere? Sometimes experiencing a local custom or event may be worth some crowds. At least on a cruise, you have the breathing space of your ship to return to.

EDIT: I looked at your other post. Cadiz has Easter brotherhood celebrations. The other ports most likely less so. However, it would be prudent to check when British school holidays are. That Spanish coast gets a lot of British families during their 2 week break.

All schools across Europe have Easter holidays then, not just the British, making travel and accommodation prices rocket in addition to any festivals.

It really depends on where you´ll plan to visit. Easter in Spain is celebrated from Th-Mo in some places, in others it´s Th-Su, and many places offer beautiful processions. Those places more well known (Seville, Málaga) for their processions will be packed...there are other places equally fantastic but with much less crowds.