Oh dear, oh dear! Two comments sprang automatically to my mind.
Gransnetters frequently wonder why there are so few men contributing to the site, but when one does come along, he gets very short shrift.
And I am not at all surprised he hasn't wanted to comment on the predominantly snide remarks made to him.
NatUni: you and your wife need to discuss this.
You need to know whether she is finding this child-care routine tiring and if that is why there is no longer "time" for intimacy between you when she is at home, for going out, or for inviting friends in, or whether there are completely different reasons for this.
Has your wife retired and did she take on the care of the grandchildren because she was bored at home, while you work? Or did she and the other gran agree because the children's parents cannot afford child-care, rather than because they really wanted to?
How long is this arrangement for? A five year old might be at school in the UK, but in no other country I have heard of. Six or seven is the more usual starting age.
In your place, I would find it unreasonable if this arrangement is expected to last until the youngest is at school.
Perhaps you should start the talk with your wife, by telling her what kind of things you would like to do when you retire and hear her plans for the time when neither of you are working.
When will that be?
Then lead on to the present state of affairs.
I took your description to mean that your wife cares for the children 3 days a week one week and 4 the next and the other grandmother does the same. If this is the case the children's parents seem to be both working a seven day week - or are they leaving the care of the children to the grandmothers when they are off work as well?
I can see that this schedule plus driving back and forth might well be too tiring for your wife, but in that case she needs to decide whether her grandchildren, or helping your daughter or son is more important to her than the state of your marriage.
In other words, I fully understand your concern, and do not think you are jealous or unreasonable, but justly concerned about your and your wife's relationship.
One solution might be that you and she both work the same number of hours a week at the same time. You at home in your office, she caring for the children.'