Yes you need to talk with her. Never mind the loss of 'intimacy' which is probaly not related at all.
But, I agree with you, that your life as a couple should not be entirely dominated by the care for your grand-children- as I imagine the other days are for dealing with day to day things- leaving very little time for you to share doing stuff together, a walk, a meal out, theatre, a course, a trip a bit further afield, etc. And, I imagine, no holidays either- not during term-time, as she has to look after kids, and not during holidays much, for the same reason.
I have said it again and again, grand-parents' role is not to look after grand-kids and raise them. It is to help, and support, and have fun, but not full-time raising them. The expectation that that is their duty, is a totally new thing. We never ever (or did you?) expected our parents to look after our kids non-stop, and to raise them on our behalf. Help- yes- but too much is, too much.
So you need to talk about this. And take great care not to appear needy, childish and jealous.
Good luck.