engagement party attire

Dear Limo Princess;
We are having an brunch engagement party outdoors in July. How do we indicate on the invitations of a dress code? The party theme is garden tea but the couple is very young. Is "country club casual" appropriate? Any suggestions? I do not want shorts & flip flops!! Please help!!
Dear Reader,
No matter what you put on the invitations, people will wear what they are going to wear. I have seen people show up in cutoffs and a t-shirt for weddings in South Florida, and it made me shudder however the mark of a true hostess is to make sure her guests are never uncomfortable. There's a story about a First Lady who had a formal tea with very old, delicate and expensive White House china. When a guest accidentally broke her cup and was apologizing profusely, the First Lady said "Oh no--it's not your fault, they are very fragile, see?" and then smashed hers to make the point. No matter what the bridal couple's guest show up wearing, you must hide your distress and make them welcome. One can only hope that they are well-bred enough to know that "country club casual" does not include shorts and flip-flops.