Laura, I've trapped plenty of Siamese ferals! So has Leslie (Simon who's picture popped up in Jods thread today) was feral born. It would be OK to keep them caged "outside" just so long as they don't bolt out to the big outdoors! Like Moosmom said, a garage or enclosed shed even. If you do get them (and hope there's just the two) never open the cage door unless they're contained in even a basement, or bathroom! Make sure you are locked in to wherever with them, as chances are they'll trash the cage looking for an escape route. Too risky that they'll dash out and be doubly confused by a new location. Maybe bring along some catnip, and put in down near enough to check under mom cats belly and see if more than one teat's being nursed on. Any signs of additional kittens?