I found my babies were at their 'best' for the few days after birth... maybe this is natures way of giving mom a little time to heal and recover. My last baby I would have to wake up to eat because she was sleeping 6 hour stretches. She was a month early and weight loss was an issue (though not any more).
So my advice would be, bring nursery water - a couple gallons just to be safe, to ensure water is good quality.
Bring some household cleaners to make sure your space is 'up to par' in the cleanliness department. (dish soap, lysol, an antibacterial kitchen cleaner, scrubbing bubbles for the bathroom, toilet bowl cleaner)
bring lots of diapers and wipes, lots of blankets (to keep from having to lay baby on any surface without a 'barrier'), lots of patience and all the love i'm sure you already have for your new baby boy. Congratulations on your adoption! How wonderful you'll be able to bring your baby home so young.
And one last thing... relax... whatever you forget, you can run out and get. whenever I am packing for a trip I always have to remind myself that they have stores where I'm going :)