Z.A.
One of my best friends is an archeologist who has been taking her child with her on digs since they were about a year old. (Ahem, for PART of the season until just recently.)
She digs in the middle east, so the day starts very very early (3-4am) and ends shortly after noon when it gets too hot to work. Of course, I'm sure you're aware that paperwork then also takes up a significant portion of time in the afternoon.
The major problem for her is that her child (between the ages of 2 & 5) would get really bored being on site after about 2 weeks...so she started sending him home after 2 or 3 weeks. Of course, she had an onsite caregiver for her child...and one at home.
My understanding is that this is a fairly common practice for archeologists; taking young children + a caregiver with them for PART of the season, and older children + a tutor or caregiver, with them for the whole thing.
I'm TOLD it's especially helpful when they're young both for them (they get to see what mummy or daddy is doing, and then get thoroughly bored by it - which lessens their anxiety), and for their parents (they get to the point where they just want their loving, beautiful, amazing child s.o.m.e.w.h.e.r.e. e.l.s.e., being well taken care of for awhile so they can dig, and enter data, and SLEEP - which lessens parental anxiety ;)
It sounds like you've got a great situation though...since your son gets to be taken care of in country by your parents, and you even get to fly to see him (without mucking about with customs no less!) every 2 weeks.
It will undoubtedly be a wonderful experience for him and for your parents. I DO sometimes have to remind myself that it's a very GOOD thing for my son to have many people who love him. (A little bit of jealousy coupled with a dash of control freak on my part) Typically, whenever my parents are spoiling my son to tears (or disciplining him in a different way then I would, but not in a way I disagree with) when they're watching him for an extended period of time, he actually gets a little tired of it and is THRILLED to be home again with Mum. It's amazing how flexible children are. They can adapt to different parenting styles and situations quite readily as long as all the adults involved are making it fun. My own son frequently doesn't seem to even notice or care that I'm gone (I've always called every day, but some days he wouldn't want to talk, being busy doing something more interesting then talking to ME...especially when he was a toddler), but a day or two after being home gets very lovey-dovey. For us it always requires about a week of adjustment time to get back in the swing of things. And while there are ups, there are also downs. They straighten out quite quickly as long as I'm gentle with him.
I myself spent 3 months a year at my grandparents house with my siblings while my parents traveled. My sister always had a hard time for the first day or two and then didn't want to leave when it was time to go. I was always thrilled to go and then couldn't wait to go home when it was time, and one of my brothers didn't appear to ever think about it while another looked at the whole thing as a grand adventure. My point being, that while children are all different; when they're surrounded by people who love them and care for them...it all works out.
Also, even though it sounds like you're Indian, it will be an invaluable experience for you son getting to live in another country for whatever period of time. And if you're concerned about medical care at all (although India, from what I've heard has wonderful medical care), talk with your pediatrician. See if they can get in contact with a clinic your parents trust and have all of your son's records faxed over to them and get a dialog started between your son's doctor here and who will be their doctor there.
But most of all: Enjoy yourself!
~Z.