With my first I only needed the 19 week scan but opted to go for the NT at 13 weeks. Second time round dr sent me for a dating scan at 8 weeks but that was dumb put my dates back a week.... My bub was born on my Lmp due date! Actually they both were!
So...... Alls I'm trying to say is it's up to you if you want the extra scans or not. It is nice to have the reassurance at the early stages I think.
Congrats on your preg and enjoy the ride! It's the best!!!