Good for you to think of sunscreen! His white muzzle is prime for melanoma, so keeping sunscreen on is a good choice...I suggest alll year round, IMO better safe than sorry.
Thanks to everyone for all the advice! I am also a new horse owner, and the first impulse is to run out and buy all the gadgets and thingamabobs, and get broke fast! I didn't know if a blanket was a good idea or not, tho I had been told that if the horse has shelyer, a blanket is not needed. Also, if the horse is far from your house, he can (and will!) get tangled in the straps if it isn't put on correctly. I didn't know about the tail bag, either. My guys tail is long, and healthy, so I may braid it, but don't think a bag is needed in my case. Does anyone codition their horse's hooves in winter?