Microsoft’s “undocumented” but quite useful stored procedure, sp_msforeachtable, you can easily disable constraint checks on all tables in a database. Here’s how:
EXEC sp_msforeachtable "ALTER TABLE ? NOCHECK CONSTRAINT all"
To re-enable the checks after you are done, simply change NOCHECK to CHECK, e.g.
EXEC sp_msforeachtable "ALTER TABLE ? CHECK CONSTRAINT all"
Hope this helps!