My advice is do not go. Send your regrets.
The fact your boss is willing to host this party (likely with alcohol involved and resultant lowering of inhibitions), indoors in what is likely a small place for 50 people, indicates it is likely that infection control will be minimal. The door test, presumably just an IR temperature check of foreheads, is not going to do much, since most people who arrive but are infectious (if any) will not have a detectable fever.
The considerations are far greater than just you and your wife. If either of you attend but are infectious, you have a more than decent chance of giving it to one or more people you know, or their partners, and they have an excellent chance of spreading it to someone else. If you and your wife are not infected at your arrival, the chance you will be infected is not tiny, perhaps even greater than 1%. If infected at the party, your chance of spreading it to somebody else is probably best described by R number, the number you subsequently infect, and that will likely be more than 1 but less than 2.
A good way to look at this is to compare it to drunk driving. In a typical year, USA has something like 15K deaths plus many more serious injuries, caused by an estimated 150M drunk driving trips. That is 1 death per 10K trips, and most people this is a good reason to make drunk driving illegal. I suspect the chance you and your wife will suffer or cause a death is higher than 1 in 10K, with a good chance it is a lot higher.
I wonder about your boss's judgment on other matters.