Ok so if you really want to host (despite actually not wanting to...) I would personally still switch it around this year. It is not working for you the way you've always done it and working yourself to death making Christmas brilliant for everyone else whilst gritting your teeth and hating the whole thing is not a healthy way to do it.
So here is how I would do it:
Christmas Day is for you and your children this year, and possibly your mum too.
Boxing Day you have everyone over for a very chilled, very relaxed day. Buffet and drinks. Snacks and treats for the children. They can all play with their new toys together. Or do whatever teenagers do these days, if they're older.
No scheduling necessary e.g. 'lunch must be at X time or it's not proper Christmas' which is half the stress on the day itself - Helpful hint, I skipped that stress all together too by having a policy of dinner whenever it's ready, so usually served anywhere between 4.30 and 5.30. No stress, no getting up at crazy hour to get things in the oven. It helps that we have Christmas dinner late in Denmark so it's normal to me.
Just let them know what time they should be there. Sit down, relax, enjoy the children being together and let your mum enjoy it too.
That is how I would do it, because I think making a big deal of it having to be everyone together on Christmas day itself with one martyr doing all the shit work and everyone else taking the piss is just stupid, frankly.