I don't think you can require guests to wear a certain brand of clothing. You could say it is a preppy/ country club theme and they can dress to that. But Polo brand cloths are really expensive, even at thrift stores, so it could be a real burden for some guests.
But otherwise it sounds cute, just be sure to register for items a variety of price points.
I don't think its to much I love special requests on things my wedding was black and white attire only and it was amazing to see everyone in there different black and white clothes! I sat go for it just don't get upset if u have peeps show up not dressed like that!
I hope I don't get upset because my cake is going too b polo then me and my babydaddy said we will wear polo I just don't like too b tacky but maybe we should wear polo and the cake polo then everybody else wear wahh they want but still register for baby Ralph lauren
I don't see nothing wrong with the polo theme you can find polo shirts at Walmart thrift stores just won't be ralp Lauren brand ( I understand not buying the name brand due to not everyone can afford to spends money on the name brands) but a simple solid polo shirt from Walmart or a thrift store is not majorly expensive