Sexuality is not "part of the equation" when saying you are married. Except when it comes to saying you are gay and married. IANAL, but it is almost like the law was written to disproportionately harm one group and not the other. But that would mean it is a "don't say gay" law after all.
You can read the law as equally affects everyone, but that is simply false. Even if you really wanted to "well actually" the situation, I'd love for you to find a Florida da/judge/jury/whatever that would prosecute a straight, young, newly-married kindergarten teacher for have a picture of their family on their desk.
In short, it is de jure anti-gay with a thin veneer of deniability. And even if you were willing to play along with that veneer it is still de facto anti-gay.
Unless you say you are straight married.
Odds are incredibly high the kid lives in a straight household. If you just say you are married, the child will understand that your family unit is like their family unit. Without some kind of prompting, how many kids have ever asked a teacher if they are straight? It is assumed.
Assuming a gay Florida teacher was even willing to risk their job by placing a picture of their partner on their desk. Saying they are married in that situation would likely invite questions. And that is okay, kids should be able to ask questions!
The default is transparent and socially accepted. All other configurations are visible, divergent, and sexualized.
Obviously not, since married encompasses more than that. If you are married to someone of the same gender or agender, then you are still married.
8 y/o is the age of a 3rd grader. Some of the very kids we are talking about are older than the precedent. While I wish it wasn't the case, that "obviously" is doing a lot of lifting.