Is this dress okay for a wedding?

It obviously depends on the setting of the wedding...if it is a bride in a cotton wedding dress with the men in tan pants and a white shirt with rolled up cuffs (like a beach wedding...) then the first is perfect! But if it is more satin and tuxes, then go with the second!
 
I actually think both are good to wear to a wedding. I would go for the second one though just because it seems a little more fancier elegant then the 1st one for a wedding...unless its a very casual wedding.
 
Both dresses are wedding appropriate. I guess I am the only one, but I don't think dress 1 is too casual.

^ nope, you are not. I love the first one but in the green. I think red is always a bit tricky at a wedding, but then I am weird like that. depends how close you are to the bride IMO. you could wear it with navy, like a cute little navy jacket and a pair of strappy sandals, ideally in red as well. oh, and then add some nice jewellery and I don't think you would be too casual. depends if the party is during the day, type of summer wedding, or in the eve.

the second one you can dress for both day and eve - i would wear it with gold sandals, some gold jewellery and clutch.

have fun at the wedding.