Hi Gem
Knowing a lot about people (like family and close friends) can definitely make it harder to read for them, but not impossible.
I still find I'm able to read for my daughter and close friends, but doubt can creep in sometimes (ie am I being influenced because I know this about my daughter/friend? type of thing). Even though you know a lot about those closest to you, it's amazing the things that still come out in the tarot that they (and you) haven't yet got a clue about. The best test of any reading is if and when things you give those closest to you come off (without any help from you or them). Hope that makes sense?
Sometimes it helps if you try to imagine you're doing your reading for a stranger (sort of mentally block out that you know the person, so you don't analyse what you're giving so much). Concentrate more on the tarot cards in front of you and less on the person you're reading them for.
Haven't seen the Da Vinci tarot deck yet, but I've also got Ryder Waite, Morgan Greer, Herbal Tarot, Renaissance, Power Animal tarot, Vision Quest and Native American tarot packs. I love pictorial tarot decks, Ryder Waite was my mom's particular favourite and it's the deck I've used most when I've done 12 monthly forecasts, over the years. Although I do read tarot intuitively, I actually prefer using other psychic tools (ie my Osiris divination Board (not Ouija), runes and more recently power animal cards. However, I really like the Vision Quest and Native American tarot as they don't seem to 'feel' like tarot to me and I'm drawn to NI beliefs.
I was very disappointed with Power Animal tarot deck I bought recently as animal pictures are poor quality and grainey. If manufacturers had taken more time and care and produced high quality images (like most power animal cards have), then I think these could have worked well alongside other Totem/Power animal cards.
My SQ forum colleague (Enigma) has about 100 decks of tarot as well as other oracles. She's been collecting them for many years. I usually 'test drive' one of her decks before I decide to buy same, that's how I came to buy my Vision Quest pack. Our Kirsty's excellent at reading tarot and teaches this, so hopefully she'll be able to give you some useful advice.
Hope you have a lovely day xx