i'm finally getting around to running this for my mates, have leveled them up with a pre adventure & now want to hit hard as they have waltzed through every obstacle ive presented them with.

how do i run the Goblin Ambush from the perspective as rules as written? the gobs can't be surprised as they are laying in wait, so i roll stealth ( 6) & compare it to my party's passive perception to determine who in the party gets surprised. those members get attacked with advantage. im going to focus attack from biggest threat to smallest, so will attack the half orc in the party first.

my question comes now: how do the disengage & hide mechanics work? do i get to roll for surprise after every round of combat to see if the party is surprised again from the goblin archers? 2 of them are focus attacking with scimitars & then disengaging as a bonus action, disallowing any attack of opportunity from the party. so basically i can move them 15' , attack, disengage & move another 15'?

when do i roll initiative? only now do i roll initiative after the first round of surprise attack? someone please help me streamline this in my head so i can run the encounter smoothly! TiA