Hokkaido and Shiretoko in mid April

My wife and I are planning a trip to Japan from 26th of March until the 20th of April.
Our plan was to finish our trip in Hokkaido (14th until 17th of april).
While looking around on Japan-Guide and the official website of Shiretoko and the Goko lakes, there is a mention that this park only opens mid-april (https://www.goko.go.jp/multilingual_eng/faq.html).

Is it feasible to plan a Hokaido trip this time of year, or should we come back another time and spend our time in a different part of Japan?

Mid April is when winter hasn't fully ended and spring hasn't fully started. Not the best time to visit Hokkaido. If you know you will come to Japan again, it may not be a bad idea to schedule a visit to Hokkaido on a later trip.

Thank you for the reply. I was already afraid so.

Would Tohoku, something like this: https://www.japan-guide.com/e/e2400_tohoku.html
be feasible in this time of year?
Looking at the calender, it seems we would be there right in the cherry blossom time.