I have sort of been where you are now.
My son had a milk allergy show up at 13 months old once he transitioned from breast to cow milk. It ended up with us having him at Sick Kids to find out why he was vomitting up everything he ate or drank and having to be admitted for 2 weeks of tests. We were so happy to learn it was just a milk/dairy allergy.

I had my son in daycare when the allergy happened but I chose to stay with the same daycare. I decided to send all the food and drinks so that I would have peace of mind knowing what my child was getting. I still paid the same $35 a day regardless.
The allergy my son had/has is not life threatening - just leads to vomitting within minutes. Our daycare provider was so concientious though and even took a course on allergies and anaphlectic (SP?) triggers just for her own sake

It really never was an issue with me even after we moved and changed daycares. I did the same thing (providing my own food and drinks) with the new provider. I think milk allergies are one of the easiest allergies to avoid compared to nuts and the sensitivity involved in nuts/fish etc