Did some internet research last night and found that there was a train from Krakow to Warsaw, and a bus from Warsaw to Riga that would avoid Belarus. Both had very tight connections so we headed back to the Kiev train station early, but they wouldn't sell Polish rail tickets.
Found an internet cafe and did some more research. Seems that flights to Eastern Europe are leaving Kiev, but Western Europe was still closed. There was an airline ticket online that was direct to Riga this afternoon, which would catch us back up, though we would have to miss Vilnius and Lithuania this trip. Decided that this was better than 2 trains and a bus for 48 hours, so we booked it online, and took a loss on the unused train ticket to Krakow.
Also booked some Riga accommodation, then spent a lovely spring day sitting in the park, with sunshine and flowers, before heading out to the airport again late afternoon. Overjoyed to find our flight still scheduled. However, we sat around till well after flight time with no information, except that they were 'still hoping'. An hour after departure time, they announced the the flight was delayed(!), with a new time of 4am for check-in for a 6am departure, so we bedded down for the night at the airport.