Tyrone,
I agree that writing is the better option. After 25 years of researching and only having known my Grandfather when i was a young lad and thinking i'd only ever know my Father and Uncle from what was quite a large family i was given an address for the Daughter in Law of my Grandads youngest brother, she is now 80.
I wrote a letter explaining who i was and that i was trying to find out about my Grandads family and included a small tree that showed how we both fitted into the family. I also included my phone number with my address to give them the option of either meathod of contact depending on which they felt happiest with.
I only had to wait 3 days and on the Sunday before last in the afternoon had a phonecall from a woman who started with " Hello, i don't realy know how to start this but i'm xxxxxx xxxxxxx" we ended up talking for almost an hour and at the end it was as if we'd been friends for years

she said that they never realy mixed with her F in Laws family and that she didn't realise there were any relatives left around and she was quite thrilled. she also passed my letter on to one of her daughters who wrote to me at the end of last week and described her Grandfather and also expressed surprise that there were other relatives around.
A letter gives the chance for them to reflect on the past and think of things to say in a conversation wheras a call puts one on the spot and can be a bit overwhelming.
Good luck with whatever you decide to do,
regards,Tony