Is there a waiting period recommended for getting Botox after Blepharoplasty? Only 3 weeks PO, but I'm anxious to get started

Usually there is no reason not to do Botox after blepharoplasty.
However after lower blepharoplasty, particularly when the canthus has been tightened or a cheeklift has been performed, it is best to wait 3+ months. The reason for this is that some lower eyelid surgeries performed through the lower eyelid, or cheeklift procedures can weaken the lower fibers of the orbicularis muscle.
Botox could further weaken the orbicularis fibers, causing a lag in the lower eyelid and drooping.
It is best to talk to your surgeon to see if any of this applies to your procedure.
There should be no reason not to perform Botox injections in the frown muscles for any of these procedures.

Dear Jen,
You have waited long enough for the BOTOX. Typically, with Microdroplet BOTOX, I find that most people can have BOTOX about a week after surgery. However, it really helps if your injector knows what they are doing.
However, we have found that BOTOX done at the time of surgery or even a few days prior to surgery, can be subjected to abnormal spreading of the BOTOX when it is done in the immediate surgical area. This can lead to some unpleasant surprises. So waiting like you have is very reasonable.

That is a very good question and there are no definitive guidelines, only opinions based upon individual experiencea. There is no doubt that injection techniques will have an impact on the outcome. The primary concern is that if it is injected at or soon after surgery, the botox may spread far beyond its intended target due to the surgical disruption of the tissues.