Oh yeah I am 40 and I am scared to death to become 50. The truth however is that being 50 years old they still have many years of productive, meaningful and enjoyable life ahead of them. They still have time to do what they maybe wanted to do and haven’t had a chance. What you can do is perhaps is to talk to them about it and suggest seeking psychological counseling, possibly cognitive behavioural therapy (CBT). For self-study of some of the techniques, buy them the book of Dennis Greenberger, “Mind Over Mood” – this one includes an example of a similar case.
Part of the crisis could be the separation of children now that their youngest son leaves on his own. So if playing an important role in their children’s life is still important to them, you can assure them that they are still needed and loved, needed by their children and grand children, maybe talk to others and find a way to engage them more.

Sheik:
“I still feel like I’m letting them down by not finding a job yet that fits into my new career path.” You are over personalizing the issue. You are probably not finding the job because of factors that lay outside of your direct control, such as very few job opportunities. Do not condition yourself by “should”/”must” statements: “I must get a job ASAP”, “I should have found a job by now”. If it comes to you, change it to “IT WOULD BE NICE if I have found a job by now”, and you will feel a bit better.
You are probably catastrophizing the issue. What is the worst thing that can happen?
You actually have a strong backup: “I am very blessed to have a mom who can sympathize with my situation and a girlfriend who loves me unconditionally”, and is “VERY successful”.
I think your main issue is your low mood and anxiety rather than your matter-of-fact situation. Your low mood and anxiety, and perhaps lowered self esteem source from automatically irrational perception of things and you need to get out of this pattern. I recommend getting some psychological counseling. Find a therapist who specializes in CBT (cognitive behavioral therapy). Also, you can learn some techniques from the “Feeling Good” book by David Burns, especially his three column technique/daily thoughts log.

I find CBT (cognitive behavioral therapy) a very effective practical method to deal with anxiety and stress; especially the 3 column technique. Search Amazon for “Feeling good” by David Burns.