Everyone who celebrates a holiday of any kind falls under one of three categories. There's the host, there's the guest, and there's the leave-after-dinner genius who learned their lesson last year, and as a result is very protective of his or her couch and very wary of others' couches. If you haven't yet learned your lesson, you're going to need provisions.
The first thing nobody of sound conscience likes to share? Soap. Of course, my house guests have a gigantic glass bucket full of end cuts to choose from, but if you're not a soaper, you're going to want to seek out some travel-sized bars to encourage cleanliness...with a limit. Nobody wins if Uncle Jep decides to stay and finish out that 4oz bar, am I right? As luck would have it, Brooke from Firebird Bath & Body has just released her mini soap samplers for the season! You've got 6 scent families to choose from, each with 4 bars in gifty packaging. Double duty!
Another thing you're going to want some control over: oral hygiene. People forget toothbrushes, it's what they do. Then they run out and buy some plastic nonsense as a future companion for your trash can or worse, succumb to their desperation during a private moment with YOUR toothbrush. Do you really know that your sister wouldn't do that? Do you? I didn't think so. Either way, chances are there's going to be some toothbrush disposal going on at some point, so why not do a solid and provide a biodegradable option from Smiles for the People? They're design-friendly, they're sterile, they're matched brush-for-brush in charitable donations, win win win.
Now, this one's mostly for your personal sanity. Label your kitchen. Specifically, label the difference between the mugs cupboard and the glasses cupboard, the plates cupboard and the bowls cupboard, and the eating utensils and the cooking utensils, because goddammit if your mother in law rearranges your cutlery one more time, you WILL lose your shit. The perfect solution? Chalkboard decals. Temporary, but not to be ignored.