Selling ITM options right before expiration

I have a quick question…

let’s say I have options to buy 1,000 shares @$30/sh.

option expires on, let’s say, May 17th.

it is 3:30PM EST on May 17th, market closes in 30 minutes, and stock is trading at $34.

so, in 30 minutes, my options are worth $4/ea assuming no stock movement over the next few minutes.

if I put a sell order at, say $3.90 (which is slightly below market) can I be assured it will sell, or is there a chance I get stuck with my ITM options and since I don’t have 34k in my account, they become worthless.

I’m worried about the potential illiquidity of selling options right before expiration. Stock has $10 billion market cap of it matters.