I was under the impression that Karpas isn't strictly required; as long as one has something to get the kids to ask, that should be enough. This is a position shared by other Mi Yodeyans as well. By this logic, then, if someone gets the kids to ask in a different way, he doesn't need to do Karpas.
This position seems to be contradicted by two sets of halachos in the Shulchan Aruch. The first is in OC 473:6:
נוטל ידיו לצורך טבול ראשון ולא יברך על הנטילה ויקח מהכרפס פחות מכזית ומטבילו בחומץ ומברך בורא פרי האדמה ואוכל ואינו מברך אחריו
He washes his hands for the sake of the first dipping, and he does not make a blessing on the washing. He takes from the Karpas less than a kezayis, dips it in vinegar, and makes the blessing "Who created the fruit of the ground," and eats and does not make a blessing after.
No mention of "getting the kids to ask." Were it this halacha alone, I might not find this terribly noteworthy. But in ibid. §7 he does bring down the rationale of "getting the kids to ask" in the context of an entirely different obligation:
מוזגין לו מיד כוס שני כדי שישאלו התינוקות למה שותים כוס שני קודם סעודה
We pour for him the second cup immediately so that the children will ask, "Why are we drinking a second cup before the meal?"
From the fact that the Mechaber says this rationale here, but not regarding Karpas, it seems to imply that Karpas, in fact, is obligatory even if the kids ask from something else.
The second halacha is in OC 475:2:
אם אין לו ירקות לטיבול ראשון אלא מרור יברך עליו בטיבול ראשון בורא פרי האדמה ועל אכילת מרור ובטיבול השני יטבלנו בחרוסת ויאכלנו בלא ברכה
If he doesn't have any vegetables for the first dipping besides Marror, he makes a blessing on it by the first dipping, "Who created the fruit of the ground," and "regarding eating the Marror." By the second dipping, he dips it in Charoses and eats it without a Bracha.
If Karpas isn't obligatory, why doesn't the Mechaber (indeed, the Gemara) say that one should do something else to get the kids asking, and save the Marror and its bracha for later (relying on the Hamotzi to cover the Marror, rather than the Ha'adamah, as Tosfos indeed suggest we do normally)?
My first reaction to defend my initial assumption is that, for whatever reason, Karpas was accepted as Minhag Yisrael, and is therefore binding as Halacha. However, the fact that we promote the Marror to before Maggid when there's no Karpas seems to imply otherwise: just because of a minhag, even a Minhag Yisrael, we're going to perform the mitzvah in a less-than-ideal fashion?1
What, then, is the correct approach to these halachos? Is my initial assumption incorrect, and Karpas is indeed obligatory? Is my second assumption incorrect, and the fact that it's Minhag Yisrael is enough of a reason to override the ideal way of performing the Mitzvah? Is there a different solution?
1Yes, Tosfos hold that על מצות ומרורים יאכלוהו doesn't force you to eat the Marror immediately after the Matzah, but they clearly say that it's preferable.
