Mysql – How to rebuilt MySQL replication without dumping the master

First off, going from 32bit to 64bit should not have any correlation to your filesystem, so copying your DB files directly should not be a concern. Dumping a large DB could be slow, so copying the raw files is probably the best option. Are you using MyISAM, or are all your tables in InnoDB? If you are using InnoDB, you could try using xtrabackup from Percona to do a "live" backup of your database without downtime:

https://launchpad.net/percona-xtrabackup

If you're using MyISAM and downtime is a concern, what you can do is perform an rsync on the data files directly while the server is running. Run it multiple times in a row until the "changed" tables are few and rsync is quick to finish. Then, you can perform a quick shutdown of MySQL, run the rsync one last time to grab the files in a consistent state and start MySQL again. You can then copy them to your new server, start MySQL and go from there.

Hope this helps!

Usually when you do a mysql load of a dump, you disable foreign key checks, then re-enable them, in fact it might do this by default. You simply need to do the same thing on the slave for the duration of the replication.

This is an import export guide:
http://technocation.org/files/doc/2010_06_BulkLoad.pdf

Disabling foreign keys:
http://gauravsohoni.wordpress.com/2009/03/09/mysql-disable-foreign-key-checks-or-constraints/