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It could become a traumatic situation, if its not handled correctly !
Mom, with your help, should sit down and have a very trueful talk with the kids describing exactly what they are going to see, maybe even take a picture so it won't be such a shock when they see their dad.
They are at they are at the right age where if you handle it right, let them know all the things are helping dad to get better, and them its like having the worse cut or a really bad wound, you can't put a bandaid on it, but what they are doing is the best for their dad, and they must stay calm, to let dad know they are there for them.
If you or they think they can handle all that, then by all means let them see dad. We can't always protect our kids from everything or they never learn to accept some things that happen in life !
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