@Drew82 - its shit that this has happened, especially like this. Sorry mate. I am currently separating from my wife too (we share 2 kids) - and I relate to how you might feel.
You mentioned "you kind of knew it was the end" - so maybe your relationship wasn't making you happy either? I don't think what your wife has done in any way is fair or acceptable - but if you're separating (for whatever reason - be it her actions, or where your relationship was) - here's some ideas which might help;
- One thing you can control is what you do to yourself. The food you eat, the smokes... try and stay in a good healthy place. It will help you think clearer, sleep better and keep your emotions relevant to the situation. Just because your wife has made some poor decisions - it doesn't mean you need to too. You need to look after yourself.
- Think about a mid-term solution, not just a short term one. If you get a small apartment that just has your bike, computer and a bed - it might be tough to make that a place you can rebuild from. I would talk with your wife (as she is half of this situation) - and try work out a way to find a place that has the potential to be more like a home. It doesn't have to be 'home' straight away - but something you can build up, that has at least a couple of rooms, so your kids could stay the nights when your not working away. Use this as an opportunity to create "Dad's place" - and not just "where Dad is".
- Do you need to move out? Can you and your wife work around the travel you do? Can she stay elsewhere when you're at home (in the spare room), and she lives there when you're travelling? This might be an easier transition for everyone? It might also help you having the kids around - to try and maintain some sort of 'routine' (for you and them) - dinners, talking about 'other' stuff - school, friends, sports etc. You don't need to do the classic 'Dad moves out' straight away - consider other options that might work for you all.
Bottom line - this is going to be some tough times. I currently hold myself together 90% of the time, and it's often the smallest thing that brings me undone. But I focus on what I can make from this - pick myself up, and take another step. Before long, I know it will all be 'normal' again - whatever that looks like. It won't hurt forever.
You can do this. This happens every day to heaps of families. It's shit, sure, but you can rebuild yourself as a Dad, and as someone you want to be.