Gloria,
My childhood birthday cakes were just the sort of thing your FIL probably made, and you would appreciate. (This made for some awkward pauses when the other little kids saw how unlike the standard white-frosting-sugary-princess situation dessert was going to be, but it all worked out!)
I just closed my browser on these two marzipan recipes:
http://www.marzipancakes.com/recipes.htm - and it makes me think further variation might be possible. Oh, one more:
http://food.sulekha.com/basic-marzipan- ... recipe.htm - since the egg whites are added primarily as a binder, I think they could be substituted for anything liquid that's tolerated and not too drastic a flavor-changer. And of course, there's more, so much more...
When I get a little more traction on breakfast/lunch/dinner, I will definitely be up for DIY marzipan - but as always, I'm getting ahead of myself ;)
But I can't stop - this one might be where I begin:
http://www.ellenskitchen.com/pantry/almpaste.html
I'm sure the rose water is lovely, and in fact, we have some in the pantry. But I would also be willing to bet that 'water' will do the job. And this has only sugar, water and almonds as ingredients, so I wouldn't let a lack of rose water (or unwillingness to test rose water) stop me from trying!
I'll let you know if I find a commercial brand of marzipan that's soy-free, and hopefully everything-else-free as well,
Sara