Congratulations Harlee!! Im very happy for you!
Regarding telling your parents, Id say its best to let them know as soon as. Especially considering youre starting so soon. Ive found, with stuff with my Mum, whether she likes it or not, shes appreciated being kept up to date on whats going on, and appreciated my honesty. The worst thing you can do is put off telling them because youre worried, as thatll just come across as you being sneaky and lying (I can tell you that from experience...)
But again, congratulations!!!