Instead, my son and I potted on (moved some microblocks into larger blocks) and planted our larger seeds this past weekend.
When we sowed the initial batch of seeds, we simply placed them into the divots without covering them with any additional dirt or pushing them into the soil. Most of the smaller seeds (e.g. basil) managed to roots themselves pretty well in the soil. However, some of the larger seeds have a few roots pushing out of the soil and have yet to get fully rooted. We transfered them nonetheless and I'm hoping that the roots will establish themselves more firmly as time goes on.
I also reused the microblocks that had ungerminated seeds and planted some marigolds and extra tomato plants. Having learned from the first planting, I used a toothpick to make a small hole for the seeds so that the growing tip could be planted more deeply in the microblock.
My baby boy planted our peas and snow peas for me. Loved watching his chubby little fingers at work. He was trying to be so careful!
And yes, I am using some boxed salad containers as mini greenhouses because that is what I had on hand. I should really have bought more seed trays and domes but I wasn't sure how this soil block experiment was going to go and I didn't want to have a ton of trays if I was going back to buying flats of annuals next year. However, everything is chugging along so well that I'll definitely be expanding my seedlings next year.
UPATE: It's been less than a week and there are a few marigolds popping up already!