Ok, getting DH involved takes stealth. Buy everyone new festive pjs for Christmas Eve, but make his not totally festive, just cosy and lovely and exactly what he loves. Pop in a bottle of seasonal beer or suitably manly hot choc (with chilli? That's a fav of dh's here) while doing glittery Christmassy ones for you and the DCs.
Talk about your plans, the things you've found for lovely presents, the magical. Santa outing you're thinking of for the DCs, plans for family fun together. Talk out loud, vaguely look for his input, but let him mutter responses to most things. Leave the odd list around - not the boring ones (unless they're things that DH could be delegated to do), more the magical ones, notes about nice music you want to put on your iPod, reminders to get certain festive films from the library or buy them, a query to yourself about blue or green baubles hanging from the bookshelf.
Is your DH handy, and would he be interested in doing Christmas list outside? Or finding others locally to plot a route to drive after dark one night?
Ask him to look at the kids movies due out and see which might suit your DCs best to see over the holidays.
Check with him if there are favourite recipes he'd like. Or anything his DM or DF would really like as you are travelling to them.
For the cottage, get some cheap but coloured and glittery baubles, some ribbon and a short set of lights. On arrival, find some nice sticks and put into a vase. Hang the baubles, twine the lights around there or along bookshelf sect and twist ribbon in nice spots too. I also like lots of candles, like one festive shape and a load of night lights and a couple of nightlight holders, for Christmas cottages. For travelling, I've found that the I kea ones in glasses work quite well and are self contained (and nicely scented).
Festive paper napkins, festive paper tablecloth, and easy nibbles and drinks, make entertaining doable no matter what the cottage is like. We've had some challenging ones over the years, but always hosted at least 1 night for our families when we travel. Make it easy on yourself though.
Your DH may be an ongoing work for a few years, but as long as I don't talk about it too early, DH has now moved froma Scrooge persona (not about spending, just attitude&) to quietly doing lots to make it magic.