OP, how are you planning to drive?
Along 192 to I-95 - there are lots of places within the Kissimmee area to stop and get something.
Along 528 (Beach Line) - just head straight past I-95 to the PC/Cocoa Beach area and you will find places that look out over the ocean/port.
Early flight to MCO in August, we'll get a snack to hold us over, then eat at the resort or eat at the Lemon Tree for lunch in Vero, Ocean Drive...sooooo good! Great breakfast and lunch downtown Vero.
It is not very far from Orlando. You could eat there or in the area - and then get on the road. There is not much going on until you get to Vero or Sebastian. Publix also makes great subs for on the road food!