Kiev is a great city to visit. I definitely recommend visiting it. There is certainly lots to do for railway enthusiasts. There are still plenty of interesting old trains from the USSR era in service.
This thread may help:
https://www.railforums.co.uk/threads/keiv-ukraine.176645/
This thread contains a similar question that someone else asked a few weeks ago. I have written a long post in post #2 which may help with your visit. There are some other good posts on that thread as well.
Let me know if you have any questions about Kiev as i have been quite a few times.