A mysqldump will attach `ENGINE=MyISAM` and `ENGINE=InnoDB` to every `CREATE TABLE` statement.

You should be fine. 

WARNING : There is one gotcha !!!

The mysql database itself (where the grant tables reside) have different column layout between version of mysql.

You can dump all databases from MySQL 5.0 EXCEPT the mysql database.

It is much better to port the mysql grants using pt-show-grants