Now you've told your other half... now for your 'rents.
If your parents are anything like mine, their thoughts are SAFETY SAFETY SAFETY.... oh and did I mention safety? Though I was going to be travelling with a friend of mine and won't be alone, that was still their number 1 concern. This is what they said in a nutshell... "We've raised you for 26 years and we don't want anything to happen to you. What happens if something terrible happens to you and we can't find your body?!!".
How NOT to do it -
"Hi Mum, Dad. I'm going go give up my job and go travelling." BIG MISTAKE. This scenario will cause them to go ape shit which they did on me with them shouting words like safety! job! career! money! etc.
How to do it -
I left it for a while then came back to them with the following...
1) Who - who you are planning on doing this epic journey with (and what they're like if they don't know what they're like already).
2) Where - show them a list of where you are planning to go (ideally produce a map in front of them if they're not particularly great friends with geography).
2) When - timeframes! Give them an idea of how long you are going for, when you are planning to go etc.
3) How - it's a good idea to show them how much money you think you'll need for this trip and show them how you are planning to go about financing it.
4) What & Why - tell them the benefits of going on this trip... how much you really want to do this, how much of a dream it is, character & experience building etc etc.
Basically, you want to show them in a high level plan of what you are going to do and how you are going to go about doing this then keep them up date if they want on the details. This would put things into perspective for them and put them more at ease.