DD and SIL never really wanted help w/ cooking, laundry, etc. They wanted someone to take care of baby for a while, so they could tend to these other things, take a shower, or get some rest. Especially w/ the colicky one. They love their children dearly, no doubt, but needed a break sometimes, as a colicky new baby can be a fulltime job.
So I agree w/ those who say that not all parents have the same needs and to ask what you can do to help, if anything. Ok to come to "hold the baby" if you're also going to do some babycare and that's what the parents want/need. And if you tell the parents to "take a break" and don't expect them to be making you pots of tea, etc.
If they don't want any help, IMO, it may be ok to let them know you want to see your new GC. Again, IMO, it depends on the parents. I would have been very hurt if my parents and PILs hadn't been interested in being around my babies, as long as they didn't overstay their welcome. That's another thing, keep visits short unless you're in the middle of helping. Other parents prefer to be alone w/ their new child as much as possible. Just follow their lead, focus on their needs more than your own, and you'll be welcome whenever they want visitors or need help surely.