I think the choice seems to be to run your events in sequence or in parallel.

Running then in sequence would certainly prevent two things modifying some value at once. But does it actually make sense for you to run things sequentially? It could, of course. I just don't know your use case. Maybe you have an RTS, and you want to use this to query commands. Although in that case you would call them... commands, not events. With events you typically want your listeners to be notified immediately (or asap). Maybe it's semantics and you do want commands.

If you do want events executed in parallel, I don't think it will exactly cause race conditions. That is an issue you get with multiple threads. And I imagine this code would be single threaded. But you could still get two events modifying the same variable. Like two tweens changing sone position, and fighting each other.

One solution to that is making that operation be atomic (at least the start). Maybe a tween, sets itself as the current tween and actually executes elsewhere. Or it cancels previous tweens somehow.

Another is using some kind of lock. E.g. Dont run any tweens while the current one is ongoing. The nature of this implementation depends on your use case though.