Duncan Hines Golden Yellow cake mix and Pillsbury White Frosting both are milk free. Of course, you will need to double check the ingredients on the box just in case they have changed them, but I have successfully used these several times for my child. Happy First Birthday!
Just substitute soy milk - it will come out just fine. Happy birthday to your son!
Best,
Rachel
Cherrybrook Kitchen has some dairy, egg, nut free mixes and are good. (found at Jewel, Whole Foods, or Woodmans's). Pillsbury's white frosting or Funfetti icing doesn't have milk (just soy). That works for my son who had many food allergies. Also, the website www.123glutenfree.com has many good tasting mixes that are dairy free among other things. The shipping is kind of expensive, but the products are worth it for special things like a birthday cake.
I have used soy or rice milk instead of cow's milk and it comes out fine, too.
My son is sensitive to dairy and turning 1 in February. I went to the store today and got Angel Food Cake- in a box. It is non dairy!
Happy Birthday to your boy!
www.elanaspantry.com is an excellent resource for anyone with food allergies. Sometimes you can sub soy for regular milk but I think it depends on the recipe. You can try it or even better just look for a recipe that is dairy free and then you'll be more confident that your dish will turn out right.
One word of caution here - please do not sub soy for everything dairy. Somebody told me it was a big mistake, and I didn't listen. My daughter ended up being sensitive to that as well. Mix it up. Maybe try rice milk if you do soy butter. Space it out then too - or even try almond milk which is what we have to do now. My daughter would drink soy milk all day long, then would have soy butter, soy cheese, soy ice-cream. Needless to say, she had way too much and it turned into a sensitivity for her.
Good luck!