Since it is for two months, they probably would be better off at home than boarded out (less stress, less exposure to disease), but I would make sure that this person is very reliable and will be spending time with them everytime they come over, so the cats have some people time, not just food, water and a clean litterbox. Is this someone who has taken care of them for you before? Do the cats know them? If not, could they come over and spend sometime with the cats before you go and give treats, so the cats will come around and your "cat checker" can check and make sure they are all doing well?
I think that if I had to be gone for 2 months, I would have 2 people coming over (like person "A" comes over once a week, on say, Sunday, and person "B" comes over the rest of the time, and doesn't have to go on Sunday, that way if person "A" falls down on the job, you'll know, and person "A", if reliable
will have one day a week where they don't say "Oh no, was today the day I check on the cats?"-gives them one day they know they don't have to do it-if nothing else, just to be nice-2 months is a long time
), or at least have someone lined up and available to come over, in case the one whom you have coming over can't do it for some reason, family emergency, etc...
If you are using a sitter service to check on them, I would still ask a friend or relative to check on them once a week. And be sure they know where the vet's number and clinic is, and the cat carriers, just to be safe.