I agree with Gasdoc. Our son is a 4 degree. Definitely sign up for the webguy pictures as part of the Association of Graduates offering. It seemed like we knew more about what our son was going through during the Basic weeks than if he would have gone off to State U. We found a lot of great pictures of the experience.
Definitely write as often as possible. Everything we heard were the Basics lived for the mail. Expect a phone call on Doolie Day out, hopefully a few letters during Basic, and maybe even a surprise phone call from your cadet during basic. We got one and it was great, so make sure you answer the phone with any unknown caller's numbers.
We took our son to I-day and were glad we could do it. We were able to see the Swearing-In ceremony the next day (get to the chapel wall early because there are a lot of family there).
We flew out to Acceptance Day which is right after Basic. You will get to see your cadet get their new Boards put on their shoulders signifying they are now a 4th class cadet. You will be limited to a few hours after the parade and ceremony. You will see on webguy forums that squadron parents will arrange for tailgate style lunches with the cadets around the Athletic Center. All the parents that do go make sure to bring enough food to cover cadets in the squadron who could not go. We picked up about a dozen Quizno's sandwiches. After that we were able to walk around the campus a little, see his dorm room, etc. Some parents dropped off printers and larger monitors but it is up to each squadron if they allow it at that time.
Definitely go to Parents Weekend if at all possible. It was a great weekend, and your cadet will be able to stay with you. Expect a hard drop off Monday evening.
Our cadet came home for the Thanksgiving break for close to a week - and he is back already for the winter break. We are so happy to get to spend some time with him.
Hope this helps,
Bill