That route is a good plan. You shouldn’t run into much issue, just make sure you’re going to the correct letter stop at Kennedy Plaza (I think 20 is stop C and 60 is Y). I recommend you download the WAVE app, purchase 2 day passes ($6 each) and you can just wave the QR code under the reader as you get on (put your phone about 12 inches below it.) Getting a day pass is the best bet because it also covers cost for your ride back, and eats the cost of any mistakes you might make along the way (ex: in case you take outbound instead of inbound and need to catch it the other direction, or if something happens and you have to get off and get back on.) It’s definitely safe. If you’re not sure of any of it you can ask the driver, no promises that they’ll be friendly but they’ll definitely tell you what you need to know.