Surprising them means Blopp and the two guards she's flanked by all make their Faerie Fire save at disadvantage. I would argue that doubling our chances of 10 rounds attacking at advantage is worth far more than a single attack with a d4 weapon. Maybe you got away with it; we'll see. Just seems not at all worth the risk to me.
Honestly, I am thinking more story than mechanics. Story-wise, Ezraen will not be beating anybody to death with his hands, and him already having A weapon frees up Erevan to arm you and himself quicker. I am not saying that you are wrong, I am just doing what makes more sense in Ezraen's mind.
That being said, DM would it take an action to have Erevan toss me my shield and rapier, or would that be under the purview of 'interact with object'?
Well...DMAesh did describe Ezraen as 'unwise' so for good or ill it's in character, I think. Besides...if she notices it doesn't necessarily ruin your ambush. We'll just have to see what transpires after I get home from work.
I don't know, if I pull if off... still 4 extra damage on a possible crit. Might be a turning point. You don't know, and we are way beyond playing it safe. ^_^