451.3125 [ d516] Residence Inn by Marriott (S)
464.3250 [254.1] Westin - Engineering (S)
464.8250 [254.1] Westin - Housekeeping (S)
469.2625 [254.1] Westin - Service Express (S)
All four of the currently-open hotels are using radios. The Hampton Inn might be using Family Radio Service radios, or itinerant business band frequencies. The Westin frequencies are unlicensed. Here are the IDs for the Gaylord National Hotel:
463.2875 (2), 463.5625 (6), 463.6875 (10), 464.6625 (14), 464.7875 (18)
The radios used for National Harbor itself are MOTOTRBO, which cannot be monitored with a scanner. 461.7875 is a repeater, and 462.0875 is simplex. These radios are used by security, housekeeping, parking, and the marina/harbor people.