Sorry, why before other players React? This is correct, right? : I play a Witch as my first Action, and a lot of when-play stuff happens. I played an Attack, so someone can reveal Moat, Horse Traders, etc. I played a first-Action, so Enchantress kicks in. I don't see how it matters whether those happen simultaneously or not, but if not there is maybe some resolution order. I then go on to resolve the card and indeed it does +1 Card, +1 Action.
Yes, they would be simultaneous, which means we do them in player order. So first you would do Enchantress (+1 Card, +1 Action), then the others would React (and then you wouldn't resolve the actual played card). That timing doesn't seem like the intended one.
But if you mean that when Enchantress kicks in on when-play, it makes you
later do +1 Card +1 Action, then yes... that works too, and I thought about it. It would mean that Enchantress, on when-play, sets up an ability to happen
whenbefore you actually resolve the card a little later (after any
Attacks Reactions). But that explanation seems unnecessarily complex: First I play Enchantress, setting up a when-play ability for your first Action card. Then that when-play ability sets up a
whenbefore-resolve ability, and that
whenbefore-resolve ability is to make you do +1 Card +1 Action. In the end the result is the same as saying that Enchantress sets up a
whenbefore-resolve ability from the start, I think.
EDIT: changed "when-resolve" to "before-resolve, since "when" means "after".