We both have European Passports. Are we eligible to apply for a 72 hour visa?

Doreen, it's true that you don't need the entry permit for HK. However, your situation does not qualify for the 72 hr free transit policy because you take the cruise into and out of China. Anyway, if your layover length in mainland China is not more than 24 hours, you don't need the entry permit either as the 24 hr direct transit policy can be used.