You can start the executions of packages also through a stored procedure. You can dump the value of the SSIS catalog executionID to a parameter in the package and use that one in your stored procedure.

I would log to a table outside the catalog though and join it to the regular logging when you need it. You have control over the schema, while the SSISDB can change in a new version without a warning, possibly breaking your code. And it saves you all the effort of finding out where to log in the catalog 🙂