"bought pictures onto t-shirts couldn't (well, they could apply, but would be rejected out of hand for lack of "special skills")"
i agree with you completely especially making the two go together but if he tells his wife she lacks special skills, sh*t may hit the fan in a hurry lol. There may be two separate Esty shops and two separate bedroom's as well. The easy answer is two separate shops but I don't have a good answer to the big picture, peace in the family.
Go with two etsy shops if you can. Now at artisan shows or crafts markets you would want some cheaper and an assortment of goods to bring more folks to your table like klara says keep them related.