First of all, ziploc bags are made of Low density polyethylene, so the only thing they will release is ethylene, and then only if they are heated hotter than the temp of boiling water. Not a problem. I suspect the manufacturer just doesn't want the liability of saying it is safe to cook in them so they say it isn't.
Second, something you do once or twice a year on a camping trip is not something I'd worry about. If it had a slight risk, and you did it 365 days a year, then you worry.
Third, the smoke from your charcoal or wood fire is far more hazardous and so is the bacon.
IMHO... cook your eggs in the bags and don't sweat it.
One time I called the number on the side of some kind of food package to ask what would happen if I reused the plastic pan the food came in. The person I got admitted it was perfectly safe, they just say don't reuse it as some idiot will reuse it until it starts to fall
apart, get burned, and sue. I suspect this is the same kind of reasoning.