Diapers - time to potty train 21 month old boys?

The diaper saga continues...because I've noticed some adhesive lingering on their hip line from the duct tape. So, last night I thought I'd try to go without to see what happens.  Sure enough, they were both diaper-free this morning and had wet all over their cribs. sigh....what to do?  I have a small suspicion that this is a sign (along with others, like signalling to us when they're pooping during the day and interest in our "pottying") that they are ready to be potty trained.  Very young, especially for boys, but maybe we'll need to give it a try. I want to try the 3-day technique, but I'm concerned that it will be longer than 3 days with twins. I don't want to take a whole week of vacation, but maybe I could plan a 4 day weekend of "fun" times.  I just want to make sure that they're really ready for this. Maybe they just think taking their diapers off at night is a fun game, like their "take shoes & socks off during car rides" game.