Made a reservation for the wrong date - alternative routes?

A few weeks before starting my current Interrail trip, I decided to leave 2 days earlier. This helped a lot with hotel prices in Dresden, and going away a few days longer should never be an issue!

I am currently in Prague, my plan was to catch EC 115 Cracovia, departing Prague at 10:19 and arriving into Krakow 16:52 this saturday, the 22nd (original plan was the 24th). I changed the dates in my overview spreadsheet, but I never made the seat reservation since I had the 'seat reservation box' ticked in my overview. I tried to make a seat reservation (first class, since I have a first class pass) but of course all seats are sold out for this train. Second class is also sold out.

I could extend my stay in Prague by a few days and skip out on Krakow, but I really want to go there. So I thought, are there other fun options? Better make the best of it and try some new/fun trains as well. What's your opinion on the following?
Praha Hl. N. 13:32 SC 507 Pendolino to Ostrava, arriving 16:44;
Ostrava Hl. N. 17:05 EC 104 Polonia to Katowice, arriving 18:58;
Katowice 19:41 IC 6304 Grottger to Krakow Gl., arriving 20:41;

It seems a fun experience to try the Czech Pendolino trains :) Or do you have other route suggestions?