Perhaps gluten free would be the best bet if you had to choose between the two?Meals aren't usually slathered in cheese and/or butter and any offending items could probably be removed from the dish before being put together on the plate.
There's also usually an option on the regular menu consisting of plain non breaded chicken/beef/fish with vegetables which should be ok no? If there is any offending sauce or item I am sure the crew could just omit it when putting the meal together. This would also avoid any possible cross contamination issues.
You can also check the Business Elite section on Delta's website with info on the menu being offerred during the months you are travelling. You can probably get an idea as to wether you could choose some of the regular items on the menu and asking the crew to work with you. This may yield better results vs a special meal where airlines usually go for the "safest" bet, meaning pretty plain stuff.
Good luck and enjoy your four trips!