Aside from the Math U See videos and worksheets I made two helpers. One was suggested by the curriculum and those big, colourful, bristol board houses under the red dragon and behind the butterfly net are it. It's a set of place value houses for the MUS blocks. They held Harry's interest for about 4 minutes.

The second set of helpers were just some place value cards. I made a set for Catherine when she was younger and so made a set for Harry and just matched the colours of the cards to the colour of the proper MUS blocks. These he loved.

I think there's a game supplement where MUS recommends place value cards but damn it, I'm claiming creative genius on this one.
In any case he's done well with place value. I'll review it a bit this week but next week we'll move on to addition. I'm fairly sure he'll zoom through that.