What if you do some practice sessions while they are still home.. just walk in with them there..then maybe have them go outside and you walk in alone with them behind you.. so he will get to know you coming and going in his..domain. That might help rather than a SURPRISE vist, so he's not

Edit- I didn't read the responses.. I see this idea was already mentioned.. duh.
__________________
Rhonda, Bailey, Josie and my angel Bella Rue'
"Until one has loved an animal, a part of one's soul remains unawakened."
~Anatole France~