Op, so many dils fall into this trap to be the family peace maker and Diplomat and often, trying to forge a relationship that simply doesn't exist between our partners and their parents.
It's not our place, our role and its rarely a good idea unless your dh has specifically said something!!
I speak from bitter experience of course.... I couldn't understand why dh couldn't get on better with his dp, I encouraged him to take his dm out for her bday, do this /that, give this /that.
She still absolutely hates me, fil hates me, they still blame everything on me and dh never wanted me to play this role.
I should have left things as they were and saved myself over a decade of stress.
Re Xmas if you have them twice in December then your well within your rights to say no to a January /February visit.
You know you've totally shot yourself in the foot re inviting them to stay in your house! How silly! They probably preferred not to stay as well!
I also only saw gp for a few hours every so many months a year and that was more than than enough!
These people have upset you and around your wedding, refused to apologise, now you have provided them with gc, many women nowadays don't want dc, having gc isn't a "given" at all.
I hate the way people take it for granted.
They have been rude to you, they are warmer to dh brother... And yet you are the one expected to do the dogs work hosting, of course your allowed to not want too and yet feel happy about hosting people who like you and love you.
I'd sit down with dh and ask him what he really wants and what thinks.
If he's happy to see them much less on the new year, do as he says. You can't force things.