
Can you arrange for him to meet the person who will perform the home visit before hand? Maybe at the rescue centre, then they may be less of a stranger especially if they can be prebriefed before hand (on things he's comfortable/ happy to talk about and what to expect from him)
Perhaps get in touch with an Aspergers group and ask advice also? I know of a couple of members on this forum who will have excellent experience in this field ~ hopefully once Christmas commitments ease they will pop by to advise.
Good luck xx