I visit Vegas atleast 6 times a year and my hotel of choice is the Palazzo, its amazing and I am sure you will enjoy every second of it!
I have never used the off airport check in for the simple reason I dont trust it. Vegas is a very busy place, the Palazzo have 300 odd people checking in and out daily especially at the weekends and I just dont trust that the bags will get to the airport.
I do know people that have used this service and have not had any major issues, but I have heard of damage occuring to handles and wheels etc. I have once left my bags with the hotel, they take them downstairs and you collect from the basement foyer, they had trouble locating my bags and took 35 mins to find them, in the meantime I missed my booked transport to the airport and ended up taking a cab.
Check in opens at the airport from around 11am, it is advertised as 12 noon, but I use this everytime now and by 11am they are checking pax in.
Enjoy Vegas it is a fantastic place! y)