First off, i think your being a little hard on yourself. The big thing to ask is how are you "selling yourself"? If your selling yourself as a "pro" and make the customer think that you have done it all and can do much more, I think you might be in over you head a little. The customer is going to expect pro results.
Now, if you tell them that you are just starting out, or you haven't tried that type of shooting yet, but are willing to try, then I would think they would be happy with any results.
The big "W" word.. weddings.... I would be very carefull here. Seeing that i just got married and was on the customer end of a wedding photographer. Don't over-sell yourself. tell them exactly what your comfortable with and what your not. A wedding is a one day thing, there are no retakes. And there's a ballance with a wedding photographer (in my mind). You have to let the day happen, but know when to jump in and take control in order to get the best shots. I've seen some that try and take over the wedding, telling everybody how to do everything, and i've seen the exact reverse, a photographer that didn't even want to stand in front of the bride to get a shot of her walking down the isle.
I'd like to take a look at some of the photos from the pumpkin patch to see if they are savable in photoshop. (which they most likely are). Keep in mind, they didn't pay you to take the pictures, they payed your gas money to come out. I would see if they want to do it again, with the cold snap we have had here in St. Louis the leaves are really changing. One good outdoor "family" shot will be all it takes to win them over. (may i suggest forest park late in the afternoon)
Sorry that i'm going on and on.. but i think most potographers feel the same way that you do. they want to do the best they can, and get mad at theirselves when it doesn't go as planned. all i can say is... learn from it and continue on...
Rutster
Rutster.com Live Digital Photography