NM, there is NO WAY you can white lie about ziplining--it just cannot be done.
I do plenty of "white lie" stuff to get my H to sit up and take notice.
But this is a big deal--the emotion, the feeling--you can't "make it up". It will affect you in ways you don't understand if you have not done it. It will be "fake" to your H and seen as manipulating. And he will definitely smell this one a mile away.
You have the perfect excuse--say your throat was too sore. And just to let you know--it is HARD WORK. We took a friend who wasn't feeling really well and he PUKED everywhere--it was awful.
This is going to be a BIG experience that you will remember always! I'm not saying it's the same as giving birth or the day you were married, but....it's a pretty big deal. Like going up in a hot air balloon for the first time or something.