Assalamu alaikum wr wb
im not apart of this jamaat but i know ppl in my community that participate in it.
From what they told me is that most of the men that are married take their families with them. Sometimes its tough for them, but usually they go together as a family. Though if they have a young child etc, under 2 yrs or so they usually go alone the men and the wife stays at home either with his paernts or her parents etc during his absense.
yes it's true he should be there for the family, but if the wife approves and gives her permission for him to do this dawah for the sake of Allah swt, than it is ok..
hope that helps
though he should also be responsible in looking after his family, meaning he should perhaps leave an amount that she can get by on while he is gone, until he returns.