Marriot (north Mumbai) is far from all the iconic places like the Gateway, Taj, Oberoi or some historical British buildings - Rajabai Tower, High Court , VT Station, Marine Drive promenade from Oberoi/NCPA side ... BUT all these are in South Mumbai. Mileage/Kms wise it is not very far but traffic wise it is far. At least 1- 1.5 hrs drive one way.
At these places you must shoot on weekdays preferably Mon-Wednesday when the people traffic is less ... that too in the morning ... before lunch or better before 9am. The sun will be from the East and quite fiery.
I'd suggest stay near/in Marriott. May be if must, just in front of Entrance. There should be enough staff from Hotel to meet your reasonable needs but sun & heat will make the subject rather uncomfortable. Air conditioned indoors should give you great photo-ops for sure. Spray & Pray techniques should work. Have fun.
BTW. Next week it will be in mid 90s with humidity in mid 80s and even though they are on the ocean but not much a breeze this time of year.