Give parents time to grieve - because for them, this is what separation feels like. I had irrational feeling that I would never see them again or see my granddaughters grow up. Anger, denial, bargaining, depression, acceptance are part of this process and each stage happens - some take longer than others to deal with.
They will get over it in time but we handle grief and loss differently so there is no real formula for 'how and when to do it'
Try not to feel guilty, get them a laptop, teach them to Skype (its never too late to learn) and look forward to an exciting future with their blessing......... eventually