We did this on our own. While it was nice to save some money, more importantly, it gave us some flexibility.
At our leisure, we had breakfast on the ship, then prepared to disembark. Because most of the Disney excursions were earlier, there was no wait to disembark.
As you leave the pier, you will see signs pointing you to the taxi stand. The taxis are 15 passenger vans, so they will try to organize people to fill the vans. We shared a ride with a group from another cruise line who was going to a beach near Butterfly Farm. I believe the total for the four of us was $15. The cab driver told us the people in Butterfly Farm could call them for the return trip, or we could walk to the beach. I gave the cab driver $20.
We went inside, and ironically, we arrived just after
DCL did. We were invited to join them for the tour. After the tour, they provide a free fruit drink, and encourage you to wander around and try to get a butterfly to land on your finger. It seemed that as soon as we went back in, they were calling the DCL people to go back to the buses. At this point, the place became deserted, and we had a great time wandering around. The lady from Butterfly Farm came over and told us our cab was waitng outside, whenever we wanted to leave (my guess is the people going to the beach didn't tip, so she came for us). After a half hour, we left, and we went to the shopping area (I think it was $15 again, and I gave another $20). We stayed there until DD5 and DD7 got tired, then we took the water taxi back to the pier.
In the end, we probably paid about 85-90% of the cost of the DCL excursion price, but we got to do things on our own schedule. This was the best part.
It was not difficult at all to do on our own.