Of course it is too late now but if I might make a few suggestions. First off, I love the shallow depth of field. I wish I had a dollar for every good portrait I have seen ruined by sharp and distracting backgrounds. I also like that you did not have the sun in their faces. This is a portraiture faux pas, especially if it creates harsh shadows or causes them to squint.
I wish the image was a little darker with richer tonality. Of course doing that also presents some of its own problems. That is where fill flash saves the day. I use off camera fill exclusively, sometimes bouncing my lights into umbrellas. All of my fill exposures are done manually. I shoot for between a 20-25% contribution of the flash to the total exposure. It lightens up the faces, adds catch lights and just adds more pop to the couple.
Below is a shot of a couple Liz and Jesse I did about a year or so ago. I used one flash bounced into a white umbrella from about 8 feet away and about 20% contribution. It is barely perceptible that any flash was used, but it adds catchlights to both of their eyes and adds some more "pop" to their faces. It also helps separate them from the background, which I underexposed about a half stop intentionally. If I had it to do over again, I would also have placed a second one over her left shoulder to separate her hair from the dark background.