You cannot transfer your SPG points to any other hotel chain except Marriott, of course. Marriott would allow to book a room for 3 adults on points in Paris -- 2 doubles or say, larger room with a king and a rollaway bed or sofa bed. There is highly unlikely to see say, two queens or two kings in a room in Paris.You would have to pay €100-310 on top of points. You will need 11,667 SPG points for 35K of Marriott points. The cheapest Marriot deal is:Paris Marriott Rive Gauche Hotel & Conference Center