I had rotator cuff repair 14 months ago, and went to WDW 3 months after surgery.
Definitely be doing everything your ortho and PT tell you! The rehab for a shoulder is so crucial...you'll hear lots of stories, like a PP said, about people doing too much and re-injuring their shoulder.
I was out of my sling by 6 weeks after surgery (everyone will be different in that regard, I imagine). BUT...when travelling and around crowds, I would wear it...partly for protection, and partly as a visible sign of "please do not run into me!"
You may be ok for parades and fireworks...esp if you can position a family member to stay on the affected side, as a buffer from other people. At 3 months out, I felt ok doing all the rides I wanted to, but was careful not to overdo it. I even rode EE. But, I was twice as far out after surgery than you will be. Probably sticking to the milder rides is best, and watch the ones that are low to the ground and take a little more balance and holding on to get in and out of the ride vehicle.
Also...take your pulley and stretch bands and do your PT exercises every day! Vacation is no time to slack off!
Good luck!