Cowboy Themed Baby Shower!

You could try to 'herd' blue balloons into baskets with sticks... then 'hog tie' them with diapers (you could use cloth diapers with safety pins to make it harder! lol)... or 'brand' (pop) them with pins attached to the end of the stick. It could be a team effort to make it more crazy and fun. You could also make 'lassos' for the mom... (think the string game... each guest gets a piece of yarn, and has to cut a length that they think will wrap around her belly. Whoever gets closest wins.) You could have a stick-pony race...

I threw a western themed baby shower not to long ago. I went to a thrift store and bought 2 or 3 pairs of beat up boots and placed small vases inside the boots (which you couldn't see) stuffed with flowers and viola! western themed flower arrangements. I also draped the tables with red and blue hankies on the tables.

maybe have them try to lasso something or do a log roll competetion (where they have to stand on a log and get it from one place to another)?

have everyone wear foam cowboy hats and bandanas? you can get those at a craft store pretty cheap.

or a knot tying competition. you cna get them form a boyscout manual

serve beanie weinies?

do you have an american royal near you?
you could go there and get ideas

You could decorate with boy theme color bandanas. Like blue, yellow, orange, brown. Joann Craft Stores usually have Foam or felt cowboy hats, which you could always use to decorate or have the expecting mother wear (maybe even write "mom to be" on it).
You could get a few small craft style hay bales. There is a baby shower game with a foot race having a potato between your legs, which would be funny.
You know how they play the safety pin game, where you can't say the word baby or whatever or you lose your safety pin. You should play that with sheriff badges. I was looking at the party stuff at walmart and they have silver badges, like 6 of them in a bag for a dollar.
If you don't want to play the game with them, they would be cute decorations.
As far as food, it doesn't have to be cheezy. Good ol' country food like baked potato (you could have a baked potato bar), pigs in a blanket (if you make them mini sized they are great appetizers), stew or hearty soups (which is always nice with a salad) would all be great to feed a crowd.
This is such a great theme, the possibilities of what or how you want it are endless. =)

hay bales and maybe a cake in the shape of a horse or cowboy hat put the punch is a whiskey thing the wooden things from the olden days and if you can come up with them tin cups for punch and a punch bowl inside of a wooden planter

Hobby Lobby has some cowboy decorations. I threw a cowboy themed baby shower for my sis, and got most of it at Hobby Lobby in the birthday aisle.

You could also do a diaper cake or wreath for a centerpiece. They can be made to any theme or colors.

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