I went ahead and finished them this week, deciding I wouldn't just use the alphabet component of the boxes. There are a lot of items in each box so we've been working on words - especially the pronunciation. I also added some word cards to the boxes so we can do some early literacy activities (even if it just starts laying foundation for the idea of coding and decoding involved in reading). I'm expanding the boxes to a few days each - doing art activities with each letter on subsequent days. Brayden has really been enjoying them so far (not surprising, I know!).
The boxes seem to give Brayden good practice on a wide variety of skills, and his articulation has already improved. I'd definitely recommend something along these lines - even if it's a way scaled down version.
Each box has a bunch of items starting with that letter, an Eric Carlyle art card (each one has an animal on the other side), an alphabet block, two coloring pages (I just found free ones online), and word cards for each item in the box (missing the first letter).
I decided not to go in traditional A to Z order. Instead, I used a Montessori approach which essentially has kids learn letters that make the most (and most common) words first. I couldn't find the exact article I used, but this explains some different order options. I (unknowingly) am using one that comes from a popular Montessori book.
After we go through each item and name is (with deliberate pronunciation), we do some of the cards. I have Brayden put the block in the square and then we sound out the word together and he finds the item. He really enjoyed this part - but the attention span for it only lasted 3-4 words at a time.
For the second day, I cut out a letter, taped it to an art pad and let Brayden go to town painting over it. We also made an animal from the letter - today we made a caterpillar in the shape of a "C." He was super proud of his masterpieces. :)