Lil Pound cake, bless your heart....it's very difficult to give you advice and to say don't worry because you will and as I am the one with PD you see things in a different way to your mother, sister or children, so I can only share how my two boys deal with it the best of my knowledge.
I was 47 when I was first diagnosed 10 years ago so my youngest son would have been 18 and the eldest 23, my youngest was still at home and is probably, well no he is the more sensitive.
He found the diagnosis very difficult, he didn't speak to me much but his girlfriend at the time told me how upset he would get and this made me feel so sad for him because I couldn't seem to help him.
As time has gone on we talk more now but he so obviously still worries alone, we were watching a video of some treatment the other day and he said does this not upset you looking at what might happen and I said no because it might not and that's not how I am now.
All I can say to you is a) Live for today what you think might happen may not, yes it is a progressive disease but everyone is different b) Talk to your mum or if you can't then write things down, write down your feelings they say it is good to write your fears down and get them out your head c) Find someone to talk to, they don't have to have expert knowledge on PD just someone who can listen
Most of all we are here, we may not reply straight away but I'm sure people will to support you.