Commas before and after "then"

Solution 1:

There are many grammatical rules for the use of commas. One of the best sources I have seen can be found at the website below. http://grammar.ccc.commnet.edu/grammar/commas.htm

Notwithstanding the article cautions that the use of a comma for "a pause in reading is not always a reliable reason to use a comma", I believe providing a cue to pause remains a very important consideration. In particular for someone reading aloud. Sadly, this is something often lost in modern day writing. The length of the sentence, I believe, is immaterial. Imagine a theatre/theater play where commas weren't used! In the example you provide, the use of a comma, in my opinion, is appropriate before the "then".

Solution 2:

In the example you provided, both are acceptable but I would say that you should be aware that in some instances adding a comma may change the meaning conveyed. A comma should also be used when listing - "We drove home, then parked the car and then finally went inside."