Take your dh's lead when it comes to dealing with MIL's- I have a particularly bad example of a MIL (ie This Morning wanted to feature her as worst MIl in the world!!!! If only I had the guts....), I always doubt my own judgement and would ahte to come between her and Dh (why bother she does that herself) so I just follow him. That assumes a supportive Dh of course, and not a toadying mummys boy.
To me, the ultimate Christmas is the one laid on by my Dad (he takes over from Mum at Christmas), and you know what? no starters, no table dressings, no napkins unless pound land had a special, no bottles of advocaat just in case and no cocktails night before- night before is pub as a family and takeaway, Christmas Day is a huge meal but no silly frills- packet bread sauce and stuffing, bisto gravy. Drinks are bought (generously!) accorsing to what will actually be drunk, they phone to ask beforehand. A few times I have done the full gourmet works here and it never matched up, coz atmosphere and relaxation is all. I wouldn't do turkey slices myself as they can be a bit synthetic in texture, but a crown roast, ham or lamb is superb! Dad often does venison as an altenative to turkey. Shove on a few store bought accompaniments (red currant jellies, apple sauce etc) and you're on a winner. I DO try to buy the stuff I can't be arsed to make for special meals at M&S, that's just personal though. I hear Waitrose is good, not one for about 200 miles though!!! LOL.
Boxing Day I MAY be cooking for mad MIL, as she is a confectioner / chef by trade it's stressful, so this year it's just salmon, new pots, beans and maybe a hollandaise. Ready made fresh hollandaise. Simple, no stress.