Yes, I believe an email noticed should be sent to allow members to know that a vote that effects the forum is going on. This will make sure that all voices that want to be heard are heard.
I would also make sure that it is stated very clearly in each vote what the yes and no are defined as. That way there is not any confusing on people voting no, thinking that they are voting not to have the change put into effect when really they could be voting that it is a minor point.
On votes that are minor points, I would propose that the forum staff (moderators and admins) discuss the change in a private forum to allow one more chance for the change to be bounced around before taking place. That way if the 50 member quota is not reached it can still be discussed by members you have entrusted with moderator and admin rights to give their final opinion on. I think the same should work is something is in the veto stage. Again, this is just my thoughts.