I would definitely call him. guys don't always like having to make the first move, or initial move like this. We're usually just as unsure as women, if not more so.

Go over and see him (about the horses or whatever); ask him if you can go over to his place after work, it's on his turf and he'll be more comfortable. Then plan on bringing dinner or a hearty appetizer and maybe some wine or beer with you. When he first sees this, he'll be thinking to himself, "Ok, she wants to hangout for awhile, not some quick "I want you to do this and get help with that blahblahblah". Also will show that you assume everything will turn out ok.

Get freshen up before hand (horse stink, yuk) but don't go to a public place ie restaurant, bar. It will place undo strain if things get heated.