abc94536,
I was in your situation before.. With my experience, when you send FEDEx send it 1 day or over night courier. it only extra $20.. But it will worth for the peace of mind. Make sure they receive it more than 90days count (Even one day).
You can go to local USCIS office and get iEAD if you donot receive it in 90days.
But I am pretty sure you will get in 90days, I got in 60days. But better you take the worst case.
My suggestion is send out the file immediatly, make sure they receive it on MONDAY.. it is worth..
YOU WON't be out of status if you donot receive EAD by 28th.. Only thing is it is not legal to work during that period. Take off from work for few days..