A clean game

I mentioned in my initial goals for this game that I wanted it to be clean enough to play with my young children.  I have been thinking about how to accomplish this and I keep running into one issue.  The hardest content to control is that which the players themselves introduce.  I really want to have players be able to be creative in weapon and vehicle design, but it was pointed out to me that it only takes one or two players to make something inappropriate or naughty to cause the game to expose people to content which is not appropriate.  In analyzing games that have an E rating like Water Warfare or anything Mario I have noticed that there is very little in the way of in depth personal customization, chat functionality, or any other way for players to introduce inappropriate content into the game environment.  Even in games where there is a very controlled environment like World of Tanks  the chat introduces a whole host of objectionable material which players just throw out there as though it normal to talk of sexual crime or of, well just plain disgusting topics.

So my quandary is how to keep this family friendly without removing the ability of players to interact, communicate, and create in the game.  Chat filters can block any profanity or similarly offensive chat,  and I will have to set up a reporting system for blocks placed in such a way that they represent genitalia, swastikas, or swear words.  I think that weapons and vehicles are going to have to be set in their design as there are too many possibilities for players to make something inappropriate there too.  I feel that because of the possible liabilities of online interactions that the minimum age will probably be 13 in order to play.