I think it's a bit daft to expect parents to put up with any kind of behaviour from grandparents just because they are the child's grandparents.
If 22an isn't happy with the way her in laws are behaving around her and her child (and it is HER child, it is SHE who is the parent and who has responsibility for her child), then she has every right to express her concern.
I too had overbearing MIL who told me she was going to wean my son at 4 months, that breastfeeding beyond a year is 'abnormal', insults my parenting decisions on a regular basis, is obsessive and thinks of nothing else but grandchildren - literally.
I made the mistake of going on holiday with in laws two months after my baby was born. BIG MISTAKE! MIL got it into her head that she was going to be involved in all the parenting decisions.
I too find the constant cooing and OTT fussing around my child very irritating and suffocating. Babies and children need personal space too. I think a bit of balanced, calm and normal behaviour is often the best approach which is just as loving as a frenzied kissing session. Yuck.
I have since distanced myself from MIL because I find her overbearing and interfering. What does she expect? How dare she try to take over! She should show more respect for my role as a parent ESPECIALLY in the beginning when most new mums feel wobbly and unsure of themselves.
22an, you have my sympathy. If there are specific things annoying you, then I suggest you have a few one line statements prepared to say in response to anything you feel is overstepping the mark. They don't have to be rude or abrupt - just firm, confident and assertive but polite.
It will get better. I feel so much better about my in laws situation as my son has got older. I'm not sure why - perhaps it's because I feel that at 18 months he can choose for himself to a certain extent what kind of behaviour he wants around him. If he wants a fuss from gps, then fine. If not, then he can chip off and find some peace without needing me to make sure he still has an oxygen supply available!