My brother is getting married in the spring. It will be an afternoon wedding in a hotel ballroom and a dinner reception directly following. The dress code has not come out yet, but I assume it is black tie optional.

I purchased this vest for DS at Nordstrom. I have no idea what to do with it. He does not have a role in the wedding, just an attendee. He will be only 18 months, so I want him to be comfortable. White shirt with black pants sounds so severe, but khakis would be too casual. Would neckwear be appropriate with this vest? Any suggestions? I am not married to the vest, it is returnable. Thank you!