Ok so this is nothing complicated and I have ideas on what to do already but I'm curious to get another person's perspective on this dilemma.
I have been very flirty with this one particular girl, the only reason I've been hesitant on making a move on her is because she is my friend's sister. He's cool with me talking to her, the only thing is that we're always hanging in a group with our other friends(4 other people) and I'm never really alone with her. I've done nothing more than cuddle with her. I think she maybe attracted to me because she is always touching me and smiling, and she's comfortable with me touching her, even her face! I've been trying to make a move on her for the past 3 weeks(we've hung out like 5 times)and the last two times I saw her(friday and Saturday) were kinda lame. I was thinking of giving it one more shot and if it doesn't work I'm moving on. I want to set up a time to hangout with her one on one, but I don't want to be direct with her. I kinda play it somewhat conspicuous with her so it wouldn't be congruent with my image to ask her directly on a date. She responds well to most of my compliance tests(she does stupid shit I ask her to do) so I was thinking of inviting her over to my house to play video games(she will most likely want too, even though she hates it

), but I dont really plan on playing video games for long. I was thinking of getting food then a walk or a movie back at my place. I want to keep it simple.
What do you guys think? Valenties day is coming soon so I don't know when I should invite her over(before Thursday/valentines day/or after valentines day)?
Basically,
1. how do I ask her out on a date without making seem like a date?
2. what are good date Ideas to where we can talk(get into comfort), then escalate?
3. When should I do it?