A couple of notes on first round of combat:
Jusika, I forgot that because you're attacking from a hidden spot, you get to add your sneak attack die to your damage roll. I rolled 1d6 for you and got a 3, to give you first attack a total damage of 6! Nice move!
Callan, let's assume your shield was already on. We can describe what Alfrey did as taking the Dodge Action, which means all attacks against him this round are at disadvantage (you roll two d20s and take the lower result). Good idea!
Pitrio, good tactics but there is no more delaying your turn in 5e. The only way to postpone your action is to ready an action and wait for the specified trigger. Using this action burns your reaction, but does not change initiative as in previous editions. There is actually no way to jump around the initiative order (temporarily or permanently) at all at this time in 5e.
Here is a description of the ready action.
We can basically simulate what you're trying to do with "readying" a javelin throw, and like you say we will trigger it after Halimar's spell goes off. Sound good?