1. I would definitely run Call of Cthulhu rather than Trail of Cthulhu for new players. The "spending" mechanic could be a little hard for new folks to grasp, and let's face it, some people just don't much care for that style of game. I would also recommend playing 6th Edition CoC, instead of 7th Edition as a starter (though I think 7th is great, it has more complex mechanics that could bog down new players).
2. For an intro scenario, I recommend either "The Haunting" (but watch out for the players just leaving the house after the action starts!) or else "The Edge of Darkness". You can find both of those scenarios in the 6th Edition rulebook. I personally prefer "The Edge of Darkness", since it has a more distinctively Lovecraftian feel, and also a lower likelihood of the players making a "failure state" decision, where they don't get to see the end of the scenario. I do think "Bryson Springs" is good too, but it could be a little tricky for you to apply game mechanics to it if you're not a very experienced GM.
3. Whatever you choose, here are some general tips:
- If you have time, do character creation with the whole group. The process of character creation will massively help the players understand what the character sheet means and how to use it in play.
- Byakhee is a great piece of software for creating investigators. If you would rather create pregens rather than do character creation with the group, I highly recommend it.
- Take the time to explain game concepts both before and during play.
- Don't worry about them not being familiar with Lovecraftian stuff. I actually think the game is better with folks who aren't familiar with it. All you need to lay out is the basic mood and theme of the game: ordinary people encountering powerful and dangerous supernatural threats that are both physically and mentally overwhelming, and confronting them with knowledge and preparation rather than power.