Why do you want to sacrifice the new plants for the kale that is going to bolt, anyway?
The young plants need all the light and heat they can get to make a good start.
Harvest the kale and freeze it. Plant the tomatoes and cucumbers in full sun. Sow more kale later for fall/winter harvest.
With a couple of small beds, just resign yourself to the fact that you can’t have everything, all the time, until they die of old age.