W.,
I do agree with you that your husband's parents could easily make the drive to you on Friday and then his sister and her family could drive to you on Saturday. That makes sense and I don't understand why your husband's parents aren't jumping at the opportunity to come earlier to see their grandkids and meet their newest grandkid. That is strange. You are right - his parents are choosing the convenience to drive with his sister and her family. I assume they are all going to drive together. Honestly, a 5 hour drive is a very long drive to only spend 1 or 2 nights. I don't understand why your husband's parents won't stay longer - like 3 or 4 nights??
Anyway, with all of that said, you can't change your husband's parents. Their priorities are screwed up, indeed, but this is who they are. Just make a mental note of this so you will always know/be reminded of that your husband's sister is their first priority and there is nothing you can do about it. As your children get older, they will be able to see for themselves that their grandparents don't care to spend a lot of time with them. Hopefully your parents will want to see them more! I think you should let this whole thing go b/c it is completely out of your control, so let go of this negative energy. It is so ironic b/c most people would be thrilled that they will be spending less time with their inlaws! LOL! But you want to spend more time with them, which is very sweet. Kudos to you, but there is nothing you can do about this. My inlaws are very similar to yours. Every time they come visit, they spend a LOT of time in our kitchen, cleaning up and doing the dishes when they could be spending time with their grandkids instead. Well, if they want to have fond memories of spending time with my dishes rather than spending time with their grandkids, that is THEIR CHOICE!! Too bad for all of them.
As far as cooking and cleaning - definately clean your house (for any guest/visitor, not just for them), but definately don't feel the need to cook for them!! Tell your husband you will all order in dinner and that you are not going to cook. Let us know what happens!