Choice of childcare day

Given the parents of both kids don't get along, I would not suggest that arrangement or even think of proceeding with it

Notjustaprettyface - I can understand why you would like the cousins to meet up and play together. I am exactly like you. Fortunately, the two d.I.ls get on well and meet up often with the children for ‘play dates’. A chance for them to discuss their m.I.l. (Me 😂)

Child ready has daycare. Your offer, if it helps DS in any way should be taken as a generous gesture. If day doesn't fit, you at least offered.

Apologies for not reading all the way through but my first thought was about the Childminder. She may not be willing to have your DGC for fewer days in the week/or that arrangement of days so the place might be lost altogether if she needs to fill all 5 days of the week.

I have my grandson two days a week Monday and Friday but Friday is all night my other grandchild she goes to a childminder my daughter inlaw said she wants me to stay nanna not nanny lol no I don’t get paid in cash I get paid in love. Don’t know why anyone would expect to be paid unless it was towards day trips etc i used to give my parents cash if I knew they were taking mine to zoo etc but I knew they didn’t like taking it but money went on my kids anyway.

I don’t think being paid or not is at issue here, but convenience to OP

beware of interfering.
sounds like you are trying to correct the family dynamic, in your eyes.
no.
might alienate both parties.

If there are difficulties between your children there may be resentment if they think you are trying to get their children together in order to get the siblings together. In the circumstances it’s best avoided.