No, its your surgery you're paying for, its up to you, they'll advise you whats "best" in your particular situation but they won't force you to choose one over the other. In reality the chance of the flap being dislodged is low after its healed, its marginally weakened vs a normal eye but its not like a tap to the side of the head will cause it to fly open. They can of course choose not to treat you if they think its not worthwhile/going to work/too risky, that will be less about the type of laser treatment you have and more to do with condition of your eyes, hugely high perscription, or various other things.
The flap re-opening isn't a particularly big deal anyway, likely a case of getting to an eye doc, having it repositioned, drops for a couple weeks again to fight any potential infections, flap resealed(thats a complete guess).
As for wavefront, the most basic surgery deals with your perscription and eye shape and thats it, wavefront does an extra detailed scan of all the minor imperfections in the eye and will try to correct for them giving a better final outcome. Wavefront is supposed to help with things like halo's, night vision, floaters, and generally improve the outcome.