Scheduled Maintenance questions?

Got an oil change today at my regular local shop. Definitely needs front brakes and going back next week. There were some other things indicated as probably due for maintenance on the report they did, and was wondering how important they are, if they are really due. Car is a 2012 Mazda CX-9 with 190k Miles. I bought it from my brother about five years ago and have put 50k miles on it. I believe he did several of these right before I bought it, but I have not done any of them since (and the shop has never mentioned them before today). Spark Plugs Serpentine belt (they did not say it was worn, just indicated by milage) Transmission fluid Coolant (actually, now that I think about it, I had that done last year when my water pump failed) Brake Fluid Everything is running fine, although I have noticed my mileage is off a little from when the car was newer. I figure It's probably time for the transmission fluid, not sure about the rest. Thanks in advance