My in laws ruined 8 consecutive Xmases in a row acting like this, and they too stay at least 7 days whenever they come. One year, we went to see my family, and they insisted on staying in our house while we were gone so they'd be there when we got home. My hubs never stood up for me. It was all his MIL's wishes all the time. She had her husband standing up for her AND my husband standing up for her. Finally I grew balls and forbid it myself and everyone hated my guts and I didn't care.
You cant' say anything this year for next year. Let it go and get through this year. Then put your foot down to your husband for next year stating that after x Christmases in a row, it's someone else's turn, even yours, to have a quiet family Christmas. Then send a card or email saying "Thank you so much for coming this Christmas and last Christmas. Just for the sake of politeness I'm letting you know in advance that next year we are having our first quiet family Christmas together, just giving you enough notice so you won't be surprised to be missig our corny tradition."
There's really no way you can say it without offending people, but either that and you'll never have a say or a nice family Christmas. Your husband sounds like the type to not care how you feel about it. Remind him whoever he sticks up for in life is who he will have to grow old with him on the front porch and if he wants that to be his brother, then fine.
Offer to let them come stay a different time of year, and his bro has the girlfriend, he's not home crying alone in a beer-they think Christmas is corny anyway.
My husband eventually gave up fighting me about Christmas, and since we have the kids now, the in laws aren't as forceful because they don't want to lose kid privileges for their other WAY TOO MANY long visits per year.
If you're going to be firm on Christmases from now on, then let this one go as "the last one for a while" and don't mention the housekeeping and dollars. If you think you may end up never escaping this tradition, then tell them You're not cooking or cleaning up after anyone but your own kids and you guys don't have extra money for them for groceries and dinners out and stuff. Then DON'tT buy stuff or take them out. Period. Maybe they'll stay a shorter time next time if they're not getting the deluxe treatment.