I think drinking bout is a bit strong. 
I went to one last night - several people did not drink alcohol. The purpose was certainly not primarily to drink alcohol, and that applies to most nomikais I've attended over the years.

@@ -19,2 +19 @@
-<gloss>get-together (involving alcoholic drinks)</gloss>
-<gloss>drinking bout</gloss>
+<gloss>get-together (usu. involving alcoholic drinks)</gloss>

All my references mention 酒を飲む

I agree that most people would probably understand [drinking party; get-together] as involving alcoholic drinks, but maybe having it like this makes it clear enough.
I would prefer this over dropping "get-together" entirely

@@ -19 +19,2 @@
-<gloss>get-together</gloss>
+<gloss>get-together (involving alcoholic drinks)</gloss>
+<gloss>drinking bout</gloss>

The English Wikipedia page for Nomikai links to a Japanese page for 宴会 where it describes 飲み会 as a gathering for the primary purpose of drinking alcohol. The English page says attending a nomikai doesn't necessarily mean you will drink alcohol, which is true, but the consumption of alcohol still remains the primary purpose of the occasion. "Get-together" on its own does not have this context, so I would suggest making that clear in the gloss.

I think 'get-together' fits the context. It refers to the common after-work gathering while drinking (or not) in Japan known as 飲み会, which are mentioned on Wikipedia.

@@ -18,0 +19 @@
+<gloss>get-together</gloss>

https://www.merriam-webster.com/dictionary/get-together#:~:text=: meeting,especially : an informal social gathering

Cannot find any source for a "get-together" ever having the implication of drinking alcohol. 

All definitions of 飲み会 I've found specify that it is for alcohol (ex. 仲間が集まって酒を飲む会。via daijis), but perhaps "drinking party" as-is is sufficient to communicate that.

@@ -19 +18,0 @@
-<gloss>get-together</gloss>