While I agree with the majority about the christmas situation I do think 1:1 adult time is very important.
I have my DS all week, and by this I don't mean I get to go to work and see other adult humans, I mean I stay up all night, take him to school and sleep for the 4 hours a day I get free.
My DS has numerous disabilities and health problems.
In the holidays I get no sleep.
DS goes to his dad's on a Friday night through Saturday and comes home Saturday night. This gives me time to establish my relationship with my DP (when he's not at work all weekend that is) but DSs dad also needs time out to be able to go on dates and eventually establish his own relationship, so he gets Saturday nights and all Sunday off. He works all week so can't really go out and date weeknights, although he probably gets more sleep than me still even if he did go out, I want his dad to be able to eventually establish a good and healthy relationship for my DSs sake.
If DSs dad wants a whole weekend off, I allow for that, if he wants to take DS away all weekend, he always can. We give months worth of notice though.
Because of this mutual respect, our relationship is a good one, I wouldn't want to go to the pub with him or anything but when DS is in hospital we can sleep in the same room together and me, DP and DSs dad can spend days in a hospital ward together chatting and getting on.
When DSs dad had a (nasty wretch) girlfriend who wouldn't give him any 1:1 time with DS we organised that he came and took DS out after school one night a week for proper quality dad and son time while she was at work.
You need time for 1:1 with your own child, your DP needs 1:1 time with both of his and you both need 1:1 time together.
This may not be every single week but you could work it monthly.
So if you've got both children all weekend every weekend one day could be both of you going off for 1:1 time with the children, your DP could have an activity on a weeknight with just your child, and maybe once a month you could book a babysitter on a weekend for you and DP to have some couple time.
Holidays like christmas need to be worked out so that all of you are happy. That may well mean compromises all round. Maybe you'll just have to write off christmas and make your own traditions the day after Boxing Day? Like a stocking each for the kids and visiting DPs family?
DSs dad has always had easter with DS, he does the egg hunts etc. I hate it, but it's only fair he gets one special occasion. Maybe you could negotiate that and make that special?