My husband and I are about the same age and also don't have kids. We've done the Western Cruise and we were /never/ bored. And we're not huge Disney fans either.
Palo is good, so is the spa and late night walks on any of the decks.
You will have lots more port days than at sea days. I /really/ suggest Sting Ray City. And there's lots of good shopping, and be along the pier at sunset in Key West.
Don't do like we did and avoid what you think are going to be 'hokey' shows in the nightclubs. We didn't go to Dueling Pianos until the last night on our cruise because we thougt it sounded fairly stupid, but the 45 minutes we did get to watch were /great/. I know DP is gone now, but this time we're going to really give the performers a chance.
I didn't notice much dancing at the dance clubs, which was a bit of a disappointment.
The big thing for us though was the relaxation. As my husband says, its the first time he's come back from a trip and not felt like he needed a day off to wind down.