My favourite blog for ideas was this Pre-sewing activities and Sewing projects for preschool age
He actually really enjoyed it. We were on a train at the time (hence the outdoors clothing and him being in a buggy - there were no seats!). I'm definitely going to try some of the other ideas from Roopa's blog posts. I think there is a niche in the market for unisex or boy haberdashery skills - maybe I'll start a boys craft club.
We ended our sewing session in a similar way to how Kit always wants to end (and often start) arts and crafts sessions, with me writing his name.