aj411 since you have hotel accommodation outside of the airport you cannot participate in the free City tours which start and finish in the airport at times outside of your stay.
I would imagine that reservations, if needed, should be made at check-in.
Several have mentioned participation in an Iftar feast after sunset.
The hotel is about 2km. from Souq Waqif, Museum of Islamic Art and one end of the Corniche. the Souq, restaurants etc open at sunset. The Museum of Islamic Art may have special opening times during Ramadan.