Louisa, there aren't many that know about sals I think. Here alot know about them because the RPAH deit that focusing on food chemicals like sals was developed in this city, the elimination diet handbook is circulated to many GP's too so you will hear GP's talking about food intolerances and food chemicals here.
I think you could easily let them save face by saying quite clearly that you "know" you children have salicylate sensitivities as you have completed careful food challenges and eliminations on yours and their diets. And that you inderstand that it is a little known area, and thet you anticipate that any questions you have about this may not be able to be answered today.
If they are open to it, you can then refer them to the Royal Prince Alfred Hospital allergy unit website and the ELIMINATION DIET handbook that can be bought from there, the Fed up food intolerance network and as well as this one:
http://failsafediet.wordpress.com/