New poster here... I have a wife and daughter who both are Celiac and have a lactose allergy, and we try and keep everything balanced. I don't eat wheat bread unless they have rice bread. I don't have cookies unless they have gluten free cookies.
Now, we have been on Carnival twice. You can request an allergy/sensitivity form and send it in to them well ahead of the cruise. Our first cruise was on the Ecstasy and the second was on the Pride. On the first cruise, we sent it in 6 weeks ahead of time, the second we sent it in 8-10 weeks ahead of time. There is possibly the size of the ships to consider as well as the length of the voyages (4 days for first, 7 days for second).
The first cruise wasn't bad. As another poster said, there was a lot to choose from for the ladies in my family, so it wasn't too much of an issue. They had not received the form in time, but they tried to help out when they found out about it. We just asked to speak to the maitre d' and he helped us as much as he could.
The second cruise we were expecting the same and were pleasantly surprised. We were ready to sit down the first time and were escorted to our table by the asst maitre d'. He told us that he was going to personally watch over our food and make sure the ladies had a great dining experience. They had special menus that highlighted which foods contained milk and wheat, which they brought in 2s and 3s to the meals so we could plan ahead. For desert, the ladies were presented with a new treat every night that was milk and wheat free.
I must say that my opinion of Carnival went way up with that cruise. With the exception of an ice cream party for the kids in my daughter's group, there was no time where they felt singled out. Actually, the wheatless chocolate cake was such a hit, they brought it again on the last night and let the other people at the table try it... and they loved it as well.
Don't be afraid to give the cruise line a call and talk to them. They are a service industry, and if they don't give you good service, they know you will go to another line that will. Personally, we are signed up to go on another cruise in November and my wife is just about ready to send the forms in.