Black pants and a dressy top might work, I think that wedding rehearsals can vary in how formal they are. This is because sometimes the wedding party will be going to the rehearsal dinner afterwards, and some people's rehearsal dinners are more formal and others' are more casual. I would play it safe with a dress that could go more or less formal. The ones you posted are fairly dressy/cocktail, and pants would tend more casual. If I truly had no idea how formal the event would be, I would go with something like this (saying this because I happen to own this dress and bought it thinking it would be good for this kind of situation haha):
http://www.jcrew.com/AST/Browse/WomenBrowse/Women_Shop_By_Category/dresses/weddingsparties/PRDOVR~97893/97893.jsp and bring a cardigan to wear over - if the event is formal, ditch the cardigan and you're appropriately dressed. If it's more casual, button up the cardigan, and you're still appropriately dressed.
Also, in the majority of social circles today, black is appropriate for weddings and wedding-related events. Heck, my bridesmaids are wearing black, as are my mom and stepmom! If your social circle is very conservative, you might want to stay away from black, though.
Hope that helps!