If you can somehow wrangle it, I'd be full steam ahead for the Christmas lunch a week before. It's your honeymoon, and given you have a great relationship with your ILs, I'm sure they'd understand that you wanted 'alone' time with you and DH. I'd be afraid that if there was an invite for lunch, that it could snowball into an even bigger gathering and then potentially an overnight thing. *hugs* Good luck on working out something that you are happy with!