My husband and I hiked the Inca Trail for our honeymoon and it was one of those amazing things that you do in your life that you probably don´t need to do again. We were in moderate physical shape but we definitely could have prepared more. It was challenging but worth the effort. Our group was small, 6 people, and our guide was very knowledgeable. The food was fantastic considering it was carried by the amazing porters. Machupicchu was, of course, amazing but there are so many other really cool ruins along the way as well.
One disappointment was that we were under the impression that the porters were carrying the sleeping pads but when we got to the beginning of the trail we were given them to carry. At first they were not that heavy but it rained one night and our tent leaked causing out pad to absorb a lot of water making it substantially heavier. When it was time to set up camp the following evening we told our guide and he exchanged the wet pad for a dryer one. I would suggest bringing your own sleeping pad if you have one because it will no doubt be lighter and will probably be more comfortable.
I would also recommend booking a room at Aguas Calientes for the night after the trek is over and hiking Huaynapicchu. You might be exhausted after the hike and could benefit from a rest and a fresh day for exploring Machu picchu and Huaynapicchu, which was another highlight of out trip. I do recommend using Inca Trail Reservations because they will repeatedly answer your questions via email so that you arrive in Cusco informed and prepared.