There are several different questions you have listed above but as a licensed contractor, former architect's rep and attorney, I will try to give you some insight from both perpectives.
The FL building code actually states the pickets on a guardrail system cannot be spaced as to allow a 4" object to pass thru. Basically you are allowed a 3 7/8" space between the pickets. The building code also dictates the amount of force and pressure a guardrail must be able to withstand. But, there are exceptions in the FL building code for existing buildings. These are noted in the Existing Building Part of the Florida Building Code, which is a seperate binder. (Please note there are alot of exceptions and criterias that must be meet and I cannot go into great detail about all of them.) Provided there is no other construction work going on in the building, the main exception that would apply to the condo association is if they can show the guardrail meets the code that was in place at the time it was constructed, they do not have to bring them up to current code; but, they do have to maintain them up to the standard of the code at the time they were constructed. It is important to note, if they take any one of them down for any reason or do any "structural work" to any of them, the balcony guardrail in which they are working on must be brought up to today's code. If any work "structural work" is done on the balconies, permits will have to be pulled and they building department (I believe the City of Rivieria Beach for Singer Island) will review for compliance.
Now, under the other view you are concerned whether someone may have a legal action "tort claim" if a child or anyone of that matter is hurt. And like all attorneys will tell you, it depends. For this type of claim, one must show the assoication had a duty to repair, they breached the duty by not repairing, causation, and damages. If during the review by the engineers turn up even some railings that are not up to standard, the condo association is now aware of the problem and if they are responsible for maintaining the balcony railings it is their duty to do so. By not repairing the balconies it can be shown they breached their duty to the condo owners (and even visitors to the condo in some cases) and the only element left to prove is the damages. Typically that is not hard to show if someone is injuried.
As stated before, this is a very brief overview and there are other arguments for the condo association side as well as the tenants in the building and even people visiting the building. I would advise once the third Engineering firm has reviewed, this be looked at closely by an attorney that understands construction/building maintainence issues that can give you a full overview of your situation.
Hopefully this helps to shed some light on your situation.