It depends on his stage and where he is now. If he is in a home he has been in al his life, it may be a hard transition. If he is already in a home, it will be rough, but easier.
The later in stage he is, the easier the move, IMHO, as the less he will remember. Just remember to bring old familiar things like pictures, music, or whatever he relates to so she has that to "know" but it is better he is closer to someone who cares.
Good luck... This is never easy!