Under the DHCP scope there should be a category called Reservations. You can add a reservation by right-clicking on this heading and choose New Reservation. Give the reservation a name which will show up in your AD DNS, assign an IP address within the scope and enter the 12 hex digit MAC address of the PDA device. Then enter any description text desired. You can choose either DHCP, BOOTP, or both. You will probably want to segment the DHCP range so that all the PDA devices are within a range. In other words, put the PDA devices in 192.168.11.200-220. The rest of the range (50 addresses) will then be available as needed for other devices.
I didn’t see the subnet mask in your listing.