I think I stumbled over something odd in SSIS using custom logging in the way as described above:
When packages are run, they log perfectly into a preset table, and everything turns up as expected in the logging table. However, when the same packages are run from a parent package, they suddenly not only produce event information on the steps in the package, but also the steps of the event-handler itself. Which causes a lot of overhead. (PostExecute fires on the actual insertion of the information, and reset of the ins/upd/del counters)
Any idea why a package called from a parent package suddenly produces events on event handler steps?