As is not often the case when dealing with government -- five minutes of your time could make a real difference.
The members of the Judiciary Committee can be found at the Massachusetts legislator directory. Each of their links leads to their contact information; the first group of members is Senators, and the second group of members is Representatives. When you call, you may simply say:
I'm calling for [Sen X or Rep Y]; I support Senate Bill 1031, regarding Humanist wedding officiants. It is important to the very significant percentage of the population in Massachusetts who identify as Humanist, secular or otherwise non-religious are able to have a wedding that meets their family's needs, with equality and dignity."If you intend to contact one or more Committee members, it is important that you do so ASAP, so that the contact has been made before the hearing.