I can help you out here.
If you take the bonus action shield shove
before you take the Attack action, then
because you only have the shield shove because you get it when you take the Attack action, then at the very same moment you took that shield shove then you
also took the Attack action; it's just that you are
resolving the shove first.
This means that if you are somehow prevented from executing your attacks, tough! You
already 'took the Attack action' because you took the bonus action shield shove granted by it. This is no harder to grasp than the fact that if the spell
sanctuary forces you to lose your attack, you have still taken that Attack action! If you can grasp that about
sanctuary, there can be no excuse for failing to grasp the same thing here!
As mentioned, I don't believe that 'taking the Attack action' and 'executing the attacks granted to me by the Attack action' are the same thing, because of reasons I laid out earlier. However, IF you believe that 'taking the Attack action' IS 'executing those attacks' (because of a Tweet JC pulled out of his backside saying so), THEN you
must also believe that 'taking the bonus action shield shove' IS 'executing that shield shove!
And even IF you choose to ignore the fact that , "if...then..." statements are
not statements of causality (making the same Error as James '@$$-pull' Crawford), and choose to interpret "if...then..." statements as if they
are statements of causality, then remember this fact about causality:-
Read that bit again: "statements of causality require the antecedent to precede
or coincide with the consequent in time". This means that the 'effect' cannot come
before the 'cause'. But it CAN come either
after the cause, or it can
coincide with the cause!
This means that
at the same time as I 'take the Attack action' I
also can 'take the bonus action shield shove' if I want!
And since you are choosing to interpret 'take the Attack action' as the same thing as 'execute those attacks', and are forced to therefore interpret 'take the bonus action shield shove' as 'executing that shield shove', if you 'take the Attack action' at the same time as you 'take the bonus action shield shove', you
must, according to that (your) definition, be actually 'executing those attacks' at the very same time as you actually 'execute that shield shove'!
So the attacks and the shield shove can certainly be simultaneous under that interpretation. And if they are simultaneous, who gets to decide in which order they are resolved?
That's right! The acting character's player gets to choose the order in which to resolve their simultaneous actions. And you can bet that we are choosing to resolve that shield shove first, thank-you-very-much!
So, however you interpret the relationship between 'taking the Attack action' and 'executing those attacks', BOTH ways lead to the conclusion that you CAN resolve the shield shove
before you resolve your first attack.
Q. E. And indeed, D.