If you haven't yet reported the accident to your insurance company, one option is to pay for the repairs out of pocket. That will keep your CarFax clear of accidents and potentially preserve your trade in quote from Tesla. Judging from the photo the repairs do appear to be quite extensive and pricey. Since your MX is already in the shop, it's most likely under a collision claim and already reported to the DMV.
Better yet, another option is to reject the trade-in on your order and still accept delivery of your new Model S. I'm sure it's a great deal with the 3 year unlimited SC miles along with recent discounts. Get the repairs done and sell your MX privately. That is the route that I would pursue. Good luck, sorry for your untimely incident.