Congratulations Jessica, that first one is always so cool to get behind you!
Here are my thoughts, hope you do not mind the honesty. Recognizing that you said it was all natural lighting, but some fill flash would have worked very well for you here. I shoot with a D50 also and the on camera flash, turned down a little, works for fill flash.
How did you meter the light? Hand held Light meter or on camera meter?
The man's hat fades into the black range and the detail has been lost, number 4 shows the hat the best.
Your lady has a beautiful smile and the poses do seem to bring out some nice personality between the two.
The background is really blown out and this could have been dealt with through some fill flash, which would have allowed for a faster exposure on your couple.
The tree is distracting in #3, hanging in front of the man's hat.
There seems to be a level of disconnect in #3. She seems to be in the moment, but he seems to be somewhere else. She is leaning into him with a big smile, while grasping his arms and he is not smiling and seems uncomfortable with his hands.
#4 - I like connections, in this shot I do not see any. You could have asked him to hold her hand that is on the tree, that would have brought them together more.
You have already accomplished the most important thing, pleasing the customer. We all learn from looking over our shots to find ways to improve for the next time. You have done some very nice things here, posing, creating some fun, connections, keep it going.