Male Fashion Advice

Years ago in a thrift store, I found the perfect pants. The formal look of slacks but without the obnoxious vertical slit pockets. The stiffer fabric and sensible pockets of jeans but with a more genteel cut. I now know these were golf pants, and I wear them every day for work.

I have an upcoming wedding, semiformal, indoors. I'm not in the bridal party, nor am I escorting anybody in the bridal party. Can I wear golf pants to this event, or do I need to go buy slacks, or even a full suit? I'm not opposed to buying a suit, I just want to know what my options are.

Edit: The specific pants I wear to work are these but I might buy something a little nicer for the event.