Hi, I'm a child protection social worker, you should be able to access specialist input from your local social work office, your kids will be going through a process at the minute which is akin to grieving, due to the 'loss' of their family, this is entirely natural. Anger and sadness are natural reactions, allow then to get them out in the open. As time progresses you might want to speak to your doctor about getting a referral to Child and Adolescent Mental Health Services, this isn't about them being 'mad' , it's about building in resilience, so please don't dismiss it out of hand.Don't push them into this, you'll know when the time is right.
You are doing all the right things, keep reassuring them, be there for them and most of all make sure they know that you love them.
Take care and I hope it works out for you and your children