"I have a question about in-laws. Not only do I have them, but they want to be involved in everything! My husbands father passed away when he was very young, so his family is small, consisting of only him, his sister and his mother. When my husband and I first met, we hung around a lot with his sister and her boyfriend. My MIL was around for everything. She is single and lonely, so this didn't seem wrong, just different. We'd have dinner with her, I'd go shopping with her and all sorts of things. It didn't strike me as odd, since I am so close with my mother. The difference is that my mother has my dad and they don't NEED me the way I feel my MIL needs us.
So, my husband and I moved 300 miles away, so the distance has helped give us some privacy. All was working out fine but then, my SIL called us one night when my husband and I were tending to our newborn child. She was 4 months pregnant and just discovered that her husband had been cheating on her for a year. This was so terrible, and seeing as I had a baby I felt even worse for her because I understood how important a partner is for this job. We dropped everything and drove to be with her for a few days to offer any type of support we could. We made this drive many times over the next 1.5 years while they reconciled and broke up many times. We always went out of our way to offer support to my SIL and MIL. They have finally called it quits and everyone is better off.
Here is the tricky part. Both my MIL and SIL are lonely single women now. My nephew and son and 4 months apart, which is great for them to play and such. Now it seem that every holiday, every vacation and every special occasion will be spent with them. Neither my husband nor I want this. We want Christmas in our own home with our three kids, we want vacations on our own. The worse part is that it is just assumed we are going up there for Christmas and it is only July! They are already planning it.
How do deal with this without looking like a heartless bitch? I want to spend some holidays with them, just not all of them."
The obvious solution is to get on match.com and find new partners for both SIL and MIL so they have something else to do with their time and don't want to spend so much with you.
OK, I'm 98% kidding about that. Well, maybe 95%.
I think you and your husband need to figure out if you want to be able to spend time alone as a family while still keeping MIL/SIL thinking you're hanging out with them, or whether you need for them to know and accept that you need your space. Either option is valid and justified, but you have to know which one is important for you emotionally so that you can decide how to proceed.
If you need for them to know that you don't want to spend every holiday with them, you're going to have to sit down and have A Talk of some sort. It may not have to be one in which you tell them that it's important to you not to spend every holiday with them, unless you need for them to know that. It could just be a talk in which you tell them that you're going to have your own little family Christmas this year so that the kids can wake up on Christmas morning in their own beds, etc.
Whatever you tell them, it's going to make everything easier if you have a definite plan to spend time with them at some other time. So, for example, at the same time you're telling them you're not coming for Christmas, you should be making plans for Thanksgiving or New Year's Day. That way they know you're not pulling away from them completely, and they know they'll definitely see you over the holidays, so it may be slightly easier for them to accept not having you there for Christmas Day.
If you don't need for MIL/SIL to recognize that you're not spending every holiday with them, you can do a gradual weaning process. The first step is to wean them from having every holiday hosted by them in their town. Claim Christmas or another holiday as yours right now, and invite them to come to you. If they object or give you any version of "but we've always had it here" you can respond that as the family is growing you want to create some new traditions, and you also want to take your fair share of the responsiblity, and not make MIL do so much work. Somewhere in there they should give in and agree to do the holiday at your house.
The next step is to mix in a holiday every once in awhile that you spend at your family's house instead of with your ILs. Once you've broken them of the idea that all holidays must be celebrated in the same way at the same location, you can miss one occasionally to be with your parents. There's no way they can argue (without looking petty) that your son doesn't need to spend time with his other grandparents.
Have you already planned a vacation for this summer for just your little family? If you have not, do so now. Even if it's only for 2 days to someplace boring. Do it, and then tell your MIL/SIL about it, and do not invite them. Tell them you "can't wait to show them the pictures" and that you'll send them a postcard. In short, act as if it's the most normal thing in the world to go on vacation without them, because it is. (If you really think they'll try to horn in on the trip, wait until it's too expensive for them to go, and then pretend that you and your husband each thought the other one had told them about the trip earlier.)
If you can get a kind of centrifugal force going of shifting the location of holidays away from their home area, going to your family every once in awhile, and taking separate vacations sometimes, you will be able to break the forcefield that's keeping you at your ILs' all the time. As long as you spend enough time with them to keep them reassured that you love and care for them, they shouldn't respond so negatively that you have to confront the issue directly.
I hope this isn't such an issue for long. It would be so nice for them if your MIL and SIL started making new lives for themselves so they could be a little less emotionally dependent on you.