Test the ropes...
I think that you should be careful not to crate your dog too long. How long so you normaly leave your dog crated? The fact that he/she is an older dog and has contol over relieving himself is to your advantage. I would just hate to see him stay in the crate all day with no food/water/potty-break or playtime BUT...
If you must I would suggest preparring him for it. If he is used to staying crated for a few hours then start putting him up at the same time EVERYDAY. Slowly increase the time that you are going to leave him in there. Also. DO NOT be surprised when you return from your trip and want to go to bed and he is going to NEED to play and eat/potty.
I know that you say that he hates other dogs (probably the older terrier comming out in him) but are you SURE that there are no day kennels that have accomadations for such as this. The kennel where I leave my dogs has one area that has individual kennels where the dogs cannot see or hear the others (they also use these areas to separate sick dogs). How about your Vet's office? So they not have an area where they board well dogs/cats?
I just hate to see you leave him in there for that period of time but just go into it knowing that you are going to have to spend time with him when you get back and you may have a mess to clean up as well!