For a normal cruise beginning and ending in US ports, you do not need a passport. Passport card works just fine. That is all I use on all my cruises. If you are planning to board or disembark in any foreign port, you may need passport to fly there.
You can postpone passport renewal so that it will expire later.
I’m a worry wart. At my age, I consider the possibility that an emergency flight back to the states exists.
True that you can postpone renewal?
(Thanks for your info!)