Philosophical thoughts:
It's not your responsibility to teach them to use their money wisely. If they're old enough to be married, they're old enough to glean that information from multiple sources -- or to ignore it altogether.
If they don't manage their money well, it won't be your responsibility to care for them in the future. If you're retired and living comfortably in your paid-for house while they're still scraping by and driving a beat-up car to work so they can make rent payments, that's not your problem. Set an example, answer questions if asked . . . but don't butt in. Nothing good can come of that.
Don't count them out altogether. I know a number of couples whose idea of "how to live life" is to spend big in their first few years of adulthood, but once they're married they think it's time to settle down, start paying attention to finances, etc. I don't embrace that thought process, but I think LOTS of people do.
Practical thoughts on the wedding gift:
A gift is not supposed to teach a lesson or come with strings attached. You don't want to buy a gold-plated pickle dish? Okay, choose something practical -- even if it's not on their official list. Everyone needs towels and blankets. Choose classic, top-quality items and know they'll actually be used. I was just looking at a towel in my bathroom yesterday, thinking, "This one's ready for the rag bag". It was a wedding gift 24 years ago.