Both my son and my daughter are married to Catholics.    Son in law turned and wedding was performed by our minister, so no issues.  

Son got married in Catholic Church, when the priest sent him all the forums, he filled out part of it saying he wasn't joining and neither would any potential kids join, and sent much of it back blank.    Figured we'd see a ruckus like we've never seen.   Issue never came up again, and the Father that performed the wedding was a gracious as could be and had a very good message.   Neither switched but some weeks they attend the son's church, some weeks the daughter in law's church.  

We left the solution of to the kids and everyone is happy with the solution.