As part of our 45th anniversary trip to Europe we will be staying in Lisbon in August 2017. We will have four full nights in Lisbon. My wife wants to visit Fatima so that is the only must do for the four days. Questions- what is the best way to get to Fatima? Any other must see sights during the rest of our time? Also, any "upscale" hotel recommendations in the center of the sights? All comments greatly appreciated.
It appears that bus service is quite frequent and takes only about 90 minutes each way. Schedules may be different on Saturdays and especially Sundays/holidays, so check carefully in advance.
In/near Lisbon--in addition to the various historic districts your guide book will describe--I very much enjoyed the Gulbenkian Museum (not large, but very nice things) and the Jeronimos Monastery at Belem. Sintra is workable as a day-trip from the transportation standpoint and has much to see, but someone who visited recently said it tends to be crowded with day-trippers in the middle of the day.
Regarding visiting Fatima. We are not Catholic and probably would not recommend it unless you are Catholic.
While in the area, I recommend two other places, Obidos and Batila Castle.
Absolutely visit the https://www.oceanario.pt/en/
If you don't have a specific plan when you arrive I suggest you take a hop-on-hop-off bus and get an idea of what there is to see. E.g. http://www.city-sightseeing.com/tours/portugal/lisbon.htm?set-lang=en