I am getting married soon and I only intended on inviting children that are part of the wedding party (three boys). It is a non-issue with most of my others guests because most of them don't have children and the ones that do will not bring them. The dilemma is this: my brother recently got married and I wanted to invite his new in-laws to the wedding, mother- and father-in-law, as well as his sister-in-law. His sister-in-law's children are not well-behaved and at his recent wedding, they cried, screamed and acted up the entire night and I do not wish to have them there because of this. My brother's wife has a child from a previous marriage and he is going to be part of the wedding and I feel like the sister-in-law will assume her children are invited because of this. Also, I am pretty sure a baby sitter is out of the question for her. How can I politely let her know that her that her children are not invited without offending any of the in-laws?
Also, on the same note, some of my single friends have expressed to me that they plan on bringing a date to my wedding. I don't want strangers at my wedding (for personal and financial reasons) and I only intended on allowing guests in a relationship, engaged, or married bring their significant other with them. What is the best way to handle this?