I once accidently ate some moldy stuff just bought from a store. I didn't even think this kind of thing would happen in a reputable grocery store. I was fine though. Don't worry too much - there isn't a whole lot you could do at this point.
If you want to sue the store, be prepared that it could be very time consuming and costly. I don't think it's worth it unless you can prove: 1) you and you child became seriously ill after you ate the bread; 2) there is a causal relationship between the mold and your illness...... When you go to court, you'll realize that people/companies do get very creative in order to win. Remember, the burden of proof lies with the accuser.