Currently triggers are not executed in a cascade update or delete. It’s a known issue since 2005 in MySQL, but still not fixed. Is there a way that it can be fixed in Percona Server?
From a comment in the first link from 2009, it may have been fixed in 6.1 (lp:6.1-fk tree). Is it possible that those changes could be merged into the Percona 5.5 branch?