I took delivery of mine last week and play golf twice a week (or more somtimes) - you can fit two cart bags in the trunk - the side lining is open on one of the sides that allows you to fit the golf bag in without removing woods/drivers. If you are talking stand/carry bags, you can certainly fit three of them in it.
As for your daughter, she will fit fine provided you are not more than 6'1. I'm 5'11 and if I adjust the drivers seat tom my driving position, I fit easily in back - not too much room but not cramped. If I was any taller, I'd have issues more with headroom in the back more than leg room. So - it's not spacious, but if you do fit, you are comfortable. The headroom issue is acceptable once you drive behind an S5 and see how well it sits low and wide on the road (honestly, followed one today that was gorgeous on the road from behind).
I have two daughters ages 3 and 5 with booster seats - no problem for them, they climb in and out like monkeys.
The only real issue I had when trying out the back seats was getting out (been too long since I had to climb out of the back seat of a 3 door coupe) - probably just gets getting used to.
Hope this helps - golf bags was a major consideration for me when purchasing - not a problem at all.
Hope this helps - talking from someone who knows the problem well.