I've never served breakfast but did stupidly allow one family to bring breakfast if the kids hadn't finished. I will never do it again.
A) They arrived at 8am, there's no reason why the kids can't eat before then
B) They brought crap - captain crunch or fruit loops or another sugary cereal that my kids got jealous over
C) Sometimes they'd show up with a plain piece of bread and expect me to toast it and put something on it, which doesn't seem like a big deal, but the time and jam/margarine/wow butter whatever really added up
D) I make sure to always feed my kids a large healthy breakfast, and it pissed me off to see these kids show up with crap. A few times the older boy (6) actually showed up with a baggie of 3 cucumber slices for breakfast! Another time it was a boost chocolate shake. Usually it was crappy sugary cereal. I wanted to serve them real breakfast but didn't want to be out money for it.

Also, I agree with the above posters that pointed out the age of the 12 month old. At least the boys I had could feed themselves without me hovering over them. You can't trust a 12 month old if you need to take your toddler to the bathroom or go dress them, for example, and it will eat up time in the mornings.

If you want to try it, I'd ask for $5 more each for you to serve your own food, and do it for a trial 2 week period. You may find the mornings getting too hectic with other kids arriving and everything.