How To Make Jeans Look Semi Formal Dresses From American Eagle?

Dresses from American Eagle? - how to make jeans look semi formal

I have a banquet and cheerleading is semi-formal, so no jeans, but need not sparkley dress with heels and so on.

Therefore I would like to use one of them. Are you one of these groups? How so? Do you think they are cute?

Yellow:
http://www.ae.com/web/browse/product.jsp?catId=cat1320034&productId=1396_9041&showId=1396_9041_746

purple:
http://www.ae.com/web/browse/product.jsp?catId=cat90104&productId=1396_9020&showId=1396_9020_101

I just want to know if one of these and if they see fit funny or strange. Due to the yellow image type that is large and seems to make you look fat is