I wonder if I am preaching to the converted with this cooking home school ideas page, but one of the things you may enjoy implementing is a monthly(ish!) ‘cultural food cooking’ session.
We choose a different country (or historical period) each session - and then try to cook and eat a meal from that place. This has been a great success with my ‘picky’ eaters and we have tried lots of foods we wouldn’t normally eat. It has been fun thinking up new ideas or incorporating our current interests - for example, during the Gold Rush the miners ate ’sow-belly and beans’ or ‘Bear steaks’!! We declined both and settled for a cowboy meal of sausages, beans and rice instead!
You may also try, where possible, to adopt the table manners of the country/culture whose food you are eating. I haven’t found a comprehensive site for this, but a google search usually unearths the information you need. There are also lots of recipes on the web, although we did find a Round the World Cookbook to be useful - I think the current version is: Internet-linked Children’s World Cookbook (as per the image), or for vegetarians Vegetarian Cooking Around the World
If you fancy trying this, but don't know where to start, then there is an e-course at Universal Class, but here are some of the more unusual ideas we have used :