I am just wondering when poor jellybean (along with countless other unsung caring heroes) are meant to have any downtime, and a chance to recharge their batteries.
To those who are poo-poohing her daughter's request for her mum to help, because they just got on with it, I say congratulations and well done you. But you are not the OP's daughter, and your children are not her children. The OP's daughter for whatever reason, feels she needs a bit of additional support. So she turns to the person she trusts more than anyone else.
To those saying that jellybean should take her husband with her - are you serious? He needs a ton of care, which jellybean would presumably still have to provide, alongside supporting her daughter.
I think taking him with her would just about break her in two. Likewise with the suggestion of the daughter and the twins coming to stay with her.
Jellybean - of COURSE you want to be with your daughter and the babies, and if it is at all possible (financially) I think you should organise care for your husband whilst you are away.
Once your daughter is established with the babies, and has got them into a comfortable routine, then if it is logistically possible, take your husband down for a visit so he can see the grandchildren.
But I think, at least on this occasion, you should put your daughter first.