A structured wedding dress, with a bodice and full skirt in silk or satin is often a great option for a formal daytime wedding. You may also want to team these types of wedding dresses with a full veil. There are various types of wedding suits that the groom or groomsmen could wear, but a morning suit is probably the most appropriate. Wedding guest wear should be fairly strict, with women in smart dresses or wedding suits and men in formal wear; perhaps lounge suits at a minimum. Be sure to specify on your invitation if you expect guests to dress in formal wedding wear.
For more helpful resources on planning a formal daytime wedding visit these links:
Wedding Dress Codes – Explains wedding dress codes and is helpful for wedding invitations
Evening Wedding Tips – Discuss your Outdoor Wedding with other brides