If you have 23 employees, I would assume that maybe 10-12 of them, max, will probably be interested in going and have that night free. Therefore, I would simply send a memo to all saying, "[Vendor] has generously offered our company 16 box seats for the hockey game in March.  We are inviting any employees who are interested in going these seats on a first-come, first-serve basis. Please respond by (oh, say, February 20th.)."  Don't mention spouses/friends at first, until you get a head count. Then if you have tix left-over after the response deadline, you can make that offer on a first-come or a drawing basis.