You can use your TD ATM card to withdraw cash from most bank machines here (QNB, Commercial Bank, HSBC, Ahli Bank, etc.). The only ones that don't seem to work (at least for me) are the Islamic Banks.

You'll probably only need about 300 - 500 Riyals at most as you step off the plane. I'm assuming you'll be picked up and transported either to your hotel or accomodation - get them to stop at an ATM or there may be one in your hotel.

Tips - check with TD about how much they charge per foreign ATM withdrawal - the amount my bank charges makes it worth my while to withdraw the max each time (equivalent of $1000CAD per day to a max of $3000/week)

Also, as a warning, if you lose your ATM card you will have to wait for a new one from Canada. Might be worth your while to make an arrangement with the bank before you leave to send a new one via courier (2 -3 days turnaround)