Good for you for going this long!!
I too, firmly believe in an "opt out" clause for the breastfeeding relationship; if one person wants out, time to wean. :)
My best advice is this:
a) Wear a shirt that doesn't give "access", eg, a bodysuit under your pjs. This will also make it impossible for YOU to just give up and lift your shirt while in an exhausted daze.
b) If there is walking to be done, have Daddy do it...there is a reason why men don't lactate..you did this for so long Dad should be happy to participate at this juncture.
c) Before all of this, start giving your boy (if he doesn't have one already) a comfort object or "lovey", this will really help with the transition. Get him sleeping with it and hold it between you when you nurse: he will begin to associate THAT with comfort and security
d) I also like telling him gently, "Mommy milk is all gone", but I wouldn't do the "big boy" thing. Now (and this is VERY important) when you decide you are truly done and you declare that the milk is "all gone" do NOT nurse him after he cries (even if he objects for an hour, actually especially if that happens). If you do, he will be confused, and learn that if he objects long enough, he will get to nurse.IF you do the other things I and others suggest gently this shouldn't happen but if it does, make sure you mean what you say....oh, and make the last nursing session really special, and drink in it all in (so to speak)as it will be a beautiful memory for you later on.
e) Show him where the sippy cup is next to the bed if he gets thirsty. I vote against another's advice to give a bottle...why give something that you would have to wean from AGAIN?
Remember, LOTS of cuddles and reassurance...good luck!
p.s I nursed my son until after age two, so what I say above is directly from experience. :)