Went away twice over July 4th. Stayed in Capistrano Beach, CA one year (not at a Marriott) and was able to see the fireworks displays of the various ocean side cities from our resort. I'm guessing that you could do the same from Newport Coast Villas.
Stayed at the Diamond Resort (again, not Marriott) in Lake Tahoe another year and was able to see the display over the lake. Not sure if any of the rooms at Timber Lodge face the lake, but if I remember correctly, it wasn't real far from our resort.
If it's a clear day, you MIGHT get lucky and see some of the Atlantic City fireworks from Seaview.