Might be a little too late... I just found this thread!
Anyway, I have a dear friend whose son has severe peanut allergies as well. What I did was make a cake from scratch (since cake mixes have a disclaimer on the box, didn't want to risk it) and since I have peanut products in my home, I ran the dishwasher in the sanitize cycle with all my cake utensils before I started. Made sure all my ingredients had not been in contact with anything peanut. Used mostly new packages of everything (I didn't have most of the ingredients at home anyway) Read ALL the labels, made a couple 1 800 calls to companies that didn't have any info on the box. I even used a new gallon of milk for the batter (since I had carrot cake with pecans in the refrigerator). And well... did the best I could to avoid any contamination... and at the party, I made sure my friend had the epi pen handy (just in case). Everything went fine, this boy loved the cake, had seconds and even took some home.
Hope that helps...
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