Some people might argue that they were explicitly instructed to show up with just their lovely smiles. Modern etiquette would dictate that in a social situation, whether a dinner party or event, if the host had to spend time and money in order to entertain, it is expected that the guest arrive with a token of their appreciation.
Grownups, if you are at a loss as to what to bring to said occasion, a bottle of wine is ALWAYS appreciated! Should the grape varietal of wine not be what the host prefers, it can always become a re-gift. And if you have any questions about wine pairings, contact the wine guru: Stacey Blacker www.redwhitebrew.net.
Another idea is to bring a plant, as they are the environmentally-aware compromise for flowers (flowers die after a few days, but plants can live on forever). Some easy to care-for plants are: spider plants, peace plants, snake plants, cacti and bamboo.
Clearly it is inappropriate for young children to bring alcohol to an informal, adult birthday or dinner party. Instead, I would recommend having the child create an artistic masterpiece that can be handed to the host (or hostess) upon entrance to the home/event. Not only can the child utilize his/her fine motor skills and one to one correspondence in the process but parents will have an opportunity to discuss appropriate social behavior in advance.
Whether handing a bottle of wine or a picture, it is important to look the host in the eye and say “thank you for inviting me. I brought this for you.”