I would probably create the Slotted padstack and then add the extra holes in the package symbol as via's. You need to do an NCRoute to output the Slotted hole.
EMA Design Automation
We've used a similar part in a prototype design but NOT on a production board. It worked fine, but our QA/verification team wasn't involved so please review the attached footprint and make sure your team will be able to accept it.
There are DRC errors present in the footprint, but we left it up to the board engineer to resolve since this will be affected by the board's constraints (and we have a small team so it's not too hard to manage).