Potential issues migrating from SQL Server 2014 to 2012 by scripting tables and data?
You shouldn't have any problems scripting your database out and running it on the new database.  There isn't any data for foreign keys to affect.  After that you will have to be more careful to load the data in the correct order.  Lookup tables first, then data tables etc.

That isn't a huge issue since you can get the order down in test before trying it in production.  Where you may have your biggest problems is in any code/features that you are using that are new to 2014.  Follow the link and review the new features and search for them.  After that it's just testing, testing, testing.  Try it out in test and see what happens.  Document your changes, change them in production to remove any issues, and then start your move.