"We opted to have the Paris Pass shipped"
Just to clarify, please note that the Paris Pass and the Paris Museum Pass are different things. The Paris Pass is usually not thought to be a good use of money whereas the Paris Museum Pass usually is...especially if you are planning to see many museums.
Redsoxmom, since you are interested in museums, if that interest includes Monet I hope you'll include the Marmottan Museum. It's not covered by the Paris Museum Pass but it is well worth the expenditure.
https://www.marmottan.fr/en/
One way you can check to see how Louvre time slots are filling is to go to the actual ticket purchase website. It looks like tickets are available for all time slots for tomorrow - just to see how things are booking. Looking at Monday March 2 (be sure to note the calendar runs from Monday to Sunday not Sunday to Saturday) it also looks wide open with all time slots showing available.
https://www.ticketlouvre.fr/louvre/b2c/index.cfm/calendar/eventCode/MusWeb
I may use acraven's suggestion next visit to Paris. I get into overload if I spend more than 2-3 hours in the Louvre and did better in the "olden days" when you could use the Museum Pass for multiple visits. I pushed thru with a 5 hour visit last Oct including the DaVinci exhibition and it was almost too much for my brain, lol. It was my last day so I did not need to function the next day except get myself to the airport, haha.