This is a tricky situation Yoda.

I think if you do the show you're going to have to get it in writing - so they don't ambush you with your sister or mother. Salukigirl makes a good point, these reality shows are all about drama. Since hoarding tendencies are most often psychologically related, the show will naturally want to focus on this aspect. This also might be emotional for you - for example they might want to know why you're hanging onto things or what's preventing you psychologically from organizing - this might be very emotional for you.
As you said there's the family problem too. You don't want them there, but I think you're justified. After what your sister did I don't blame you. I just had a thought -imagine if you announced what your uncle did - once and for all, he would be outed.
I wonder if the TV show is going to mention your abusive husband? I'm concerned this show is going to be like a 'can of worms' and it might be upsetting for you. You really have to weigh the pros and cons. I think you should consult your therapist or doctor.