I think also if they are financially strapped with a new baby, rather than plying them with non stop presents which is very easy to do, give perhaps some supermarket vouchers so they can buy nappies and cheaper baby clothing of THEIR choice.
Also offer to perhaps batch bake for their freezer or pick up shopping as you are going to get your own is always a good one - anything that can save them time but can impact on them so easily is always acceptable - you are being helpful without being too intrusive.
And finally, don't give advice - as Brendawymms has said they have to learn by their mistakes, but perhaps just say that if they want any tips they can just ask - and don't forget there are probably two sets of grandparents involved so your way might not be the one they take,
To ask for your experience of scalp cyst removal?