Play Horseshoes
A classic game of the old West is horseshoes. The rules aren't difficult to learn and the game is easy to set up and play. Yet it is challenging and requires some skill to make ringers. All you'll need is a metal stake and some horseshoes for tossing. Clear out a space in the backyard and start the game. Make sure everyone stands clear so no one is accidentally hit. Players can play solo or they can form up teams. Let the fun begin.
Play Cards
One of the most common past times for cowboys in the old West was to gamble. Playing cards was common with some players making a living as a professional gambler. Set up a couple of card tables and let your guests play poker and blackjack, two of the most common games from back then. Five card draw is the classic poker game played in olden times. Since you're just playing for fun, hand out chips to everyone. To add to the game, at the end of the evening let everyone take their winnings and bid on prizes.
Pan for Gold
One of the biggest draws for bringing people out to the old West was the lure of gold, so let your guests enjoy a little gold rush fever of their own. Play a game of panning for gold. For this, you'll need a sandbox filled with sand. In it, you'll have to "salt the mine" by adding in bits of treasure to find. Of course, you don't have to supply real gold. You can use fake coins or other bits of treasure. Give each guest a strainer and a pan to try their luck.
Mechanical Bull
Depending on how much older your guests are, you might consider renting a mechanical bull. Clearly, this activity will be better suited for younger and more athletic adults, but some older and still athletic guests may want to try. Simply locate someone near you with a bull for rent. They'll come out and set up the bull and run it. It'll provide fun and excitement even for those who prefer just to watch.