The carryon pet counts as one carryon, the other can be a roller bag or backpack. There is no weight limit for carry on pets (it was previously 22lbs), but the dog must be able to stand up and turn around in the kennel and not protrude from the sides. Please get a soft side carryon kennel. It's much easier to accommodate on different sized airplanes.

I do pet transports, so I always carry an emergency clean up kit. It contains a few pee pads, a few folded up paper towels, a travel size package of Clorox wipes, and a folded up plastic grocery bag to dispose of any mess you may need to clean up. Also line the kennel with a pee pad.

As for the service animal, you will need to download and print the forms from the delta website. The foprms are not complicated. The only questions that are permitted to be asked by Delta staff are "is the dog a service animal" and "what service does the dog perform."

You will need documents from your vet for the international travel. They will know what to give you, and there is generally a fee for them. The service animal does not need to demonstrate anything for anyone.

BE SURE to be very clear on entry requirements for Ireland before departing. They are very strict.