Shoot me a message if you like re: your son's and daughter's interests, and I'm sure I can come up with some fun suggestions. The key here isn't to present this as an instead of situation (at least to your son), but get them ramped up and excited for something new.
if you'll indulge me to put on my psychologist hat a moment, children very much identify with their parents, and when they see mum and dad at cross purposes, particularly when there are arguments it creates a great deal of inner turmoil. This is why it is ideal when parents get on and they know they are loved by both.
To suggest an additional strategy, your son is likely feeling the grown up by getting to play grown up games. Use that, tell him you are worried about his little sister when you're not there, and can he make sure she feels safe and happy, just as a general thing not in specific to this issue, and make sure she can tell him if something upsets her.
Many thanks dervel, for your good suggestions. I will definitely try the Lego game strategy first - have doubts my ds will find it as thrilling as cod - but will certainly give it a go. He seems to be very defensive now about his dad and realises quickly when I am trying to get him to see an alternative point of view. Makes me feel like I am walking a tightrope - don't want to discredit his dad but at the same time, want him to realise the pastime his dad undertakes is not suitable for him and his sister. So frustrating. Really don't want him to feel he is in a mum v dad situation. :-(
Was just headed to bed, but compelled to respond to this. I'm an avid gamer myself, and there is no way on God's Earth I'd have a child playing stuff like that. I'm not sure if you remember, but there was a stink surrounding one of the Call Of Duty series (Modern Warfare 2) which sees the player potentially gunning down innocent unarmed civilians in an airport. Without getting sidelined into discussions of that specific instance, it is VERY clear to me this isn't the sort of game a 7 year old should be playing, or a 5 year old watching.
I can see two potential options here:
I would want to look into going through official channels, have a quick chat with a solicitor, maybe the mediation route. It's one thing him thinking he can hack you off, it's quite another him having to justify this sort of behaviour to third parties. It also sets quite the pattern of bad parenting.
However if you choose not to go down that route, you can of course get creative in other ways. Your ds presumably has interests in media more directly aimed at his age group. Well there are plenty of videogames very much aimed at that market (assuming you are not against videogaming as a whole). The Lego series of games are particularly great for this sort of thing. They do Star Wars ones that are very good which you can play together (co-operatively). Without knowing what your ex has, perhaps look at a second hand Wii (probably the best machine for family stuff and also the cheapest!), and find some stuff that's appropriate for you and both your little ones. Establish it's better and more fun if his sister isn't excluded. Then they can take it over their dad's and play proper family orientated stuff. If you play with them a little you can get a feel what is likely to become favorites for them to do, and they will be champing at the bit to play all these things with Daddy too! So maybe take this new found interest in gaming and channel it in a positive direction. I'd like to add the caveat that similar can be achieved with a couple of board games, or even something as simple as hide and seek!
I would however advocate nipping this in the bud officially. In the end you are 100% in the right to find this objectionable. I also see how heartbreaking it is to want to communicate to your son (as you would want to tell him not to stick his hand in boiling water), but feel stuck. I appreciate that divorced parents will each parent in different ways, but I stress that I think this is heading in the direction of a welfare issue for the children rather than simply divergent parenting styles.
Recently ex h has started playing call of duty with my ds (7) when he has him for sleepover. Often my dd (5) is in the room watching. He knows how strongly I feel about how inappropriate this is but couldn't care less about my feelings. He also allows my ds to watch dvds which I consider to be totally inappropriate but again, doesn't care. I actually think it gives him a lot of satisfaction to know how upset this makes me. Of course my ds thinks it's great and talks about it animatedly when he's at home with me. I've told ds I don't agree with him playing these games and that it makes me sad but I'm loathe to say much more to him in case he feels caught in the middle of myself and his dad.
I feel powerless in this attack on my ds's innocence. Would appreciate feedback from others who have been in a similar situation - any ideas on what I can do?