I'm 48, getting married next month, and I don't think that dress looks young at all. It's very elegant and understated. I'm wearing a proper A line wedding gown and don't care what people think. It's modest but glamourous and I think it's still age appropriate. It is still okay for an older person to look glamorous. Just look at some red carpet stars you like.
The second dress did look poor on the model but maybe its nicer on you.
As for people saying not to wear white over 35, wise up! Soooo many people much older look fantastic in white. Look up Carole Kirkwood's recent wedding, she looks stunning and is much older than us.
I do like that first dress, but you said you feel it's too late to get something special- if that's what you want it really isn't too late! Loads of shops do sample sales and you can leave with the dress immediately. You deserve to feel special, so make sure you do whatever you wear.