thanks for the replies, much appreciated!
just read the KC agility rules, it said that dogs over 4 calender months can entered as "not for competition", whilst competing dogs need to be 18 calendar months, and nothing said about spectator dogs.
it seems a bit cruel to the boy that he need to give up something he enjoys a lot for a new pup, especially those are probably his last agility shows ever in his life, so will see how things goes. since the entry forms need to send out, so probably will enter the shows first and decide whether to get the girl or not. if we got the girl, probably will be house bound for a couple weeks and get ready for a big move.
p.s. the pups will be going on flight probably in another month's or so, so house training for the pup isn't really necessary, she might train to do it indoor at the end of the day