Homeschooling really has very little to do with how smart you are. Lots of curriculums are online and come with tutorials, lectures, labs and so forth. Even the ones that aren't online come with study guides, and material to explain. These can all be substituted online through free resources like Khan Academy (look it up, it's awesome), and you can google or bing how to do anything. You will also find that you are relearning right along side them and that's kind of cool.
The key to whether or not you can be successful is really about how dedicated and structured you are in insisting that they learn and do their work. Following through is key. So, with that in mind, here are some questions - not for you to answer for me so much as to think about before you decided:
1. Are you prepared for the days they wake up and decide they don't really want to work.
2. What backups do you have if they are just not understanding something? You will need to set a plan in place.
3. How many hours a day are you wanting them to study? Are you going to set a schedule?
4. How will they do (given their ADD) with the lack of structure? Are you able to keep them on task without it turning into an all out war?
5. How do you plan to keep them excited about learning and motivated?
6. Will they take this experience and you seriously?
7. Do they want to do this? At their age, if they aren't on board, you are going to see some spotty, even poor, results, so you need to have their buy in.
It can be a really good and positive experience. School is not the only place to socialize them, but you do need to have other social interactions in place so that they can gain skills, not lose the skills they have, and don't begin to feel isolated.
I chose to homeschool my son because he has a learning disability that makes it VERY VERY difficult for him to learn in the main stream. He is very smart and can learn, but needs to approach it in a different way, and lots of time the schools just didn't have the time or patience to deal with it, even with an IEP.
If you want to do it, they want to do it, and you are 100% dedicated, then it can be a really positive experience. Just do a lot of study and ask your friends the questions I asked you and get some advice on how to deal with things when they get tough, because they may.