Can you have friends and family in attendance at a courthouse wedding? Do you have to send formal invitations for this type of a wedding?

Sure you can have friends and family (though probably not a whole lot of people), and since it isn't a formal wedding I wouldn't expect you'd have to send formal invites.

Most are done in chambers, so it is in the judges office, and it is not formal, also there is often no exact time for example in many courts, they hold weddings twice a day, so you go and wait in the waiting room with all the other couples until it is your turn to go in and be married,

You should call the court and ask for the max visitors.

Also remember you can normally find a local pastor to do a wedding in your home for little to nothing.