We did this
ABD and honestly were more than ready to head back by the end of the Machu Picchu day. It's a big place, but not THAT big. The guides do a really good job of taking you all over the ruins and explaining things, then after a really yummy lunch in the Lodge, you have plenty of on your own time. Some hiked up to the sun gate, and some hung around the ruins. But there's not anything to *do* there, so it's a lot of "Oh, wow, this is beautiful." Which, for my personal family, we can only do for so long.
Yes, you will miss the sunrise photos. If you are a photographer and this is a must-have for you, then obviously you would need to do a different tour. Only you can know where on the scale the sunrise falls compared to the other things on both the ABD and the other tours you are considering. I know there are even some tour companies that are mainly for photographers.
As for the walking stick: It depends on your age/fitness level. The steps are not actually as treacherous as they may appear in photos. Also, you may have seen images of steps coming up from the Inca Trail, which you will not be on if you do the ABD. From where we entered, at the main gate right by Sanctuary Lodge, there was an upward trail that wound around and included both steps and dirt path. I feel like the final climb to the highest vantage point was a little steeper, but we stopped first at a photo op and rested, and then it was only a few more steps up.
There was a lady in our group in her 70s who was in good shape, but had either had knee surgery or some balance issues (can't remember which, she never made a big deal out of it) and she used a walking stick. I think, though, that the guides provided it to her. If you are inclined to use a stick, but to only use it for this portion of the Adventure, it would be worth calling ABD and asking if the guides have access to sticks rather than you having to pack one.
Also, she used the stick after consultation with the guides and deciding she could handle the climb. If she had decided that she couldn't handle it, there was another way she could have gone in, and skipped the most difficult climbing. The guides just took us up that one path because it blocked the view of the ruins until we were above them at the best vantage point to be awed with our first glimpse. That's the Disney magic

The steps within the ruins themselves are wide stone, and were not at all difficult to navigate.
IF, though, you have issues with walking and climbing in general, and a walking stick helps you, then definitely bring one. Machu Picchu was one of the less strenuous days on this Adventure. I found it much harder to climb down into the circular farming pit, not to mention the climb back out! The hike down into the salt mines is on a narrow track that slopes down at a definite angle, and the Sacsayhuaman "walk" involves some real ups and downs as well. Hey, you're in the highlands of Peru - it's not flat!