I prefer them to be 6 (as in the last Tale of Years) partly to avoid that sort of device. I want them to be old enough to know and remember that Elves did this. If Maglor and/or Maedhros are to gain forgiveness let alone affection, I think they ought to have to earn it from children who know who they are and what they did. They should have to prove that they're sorry, and really mean it, and try to make amends. They shouldn't get off easy, or get away with lying about what happened. That means the twins will initially fear and hate them.
Half-elves have very good memories, if perhaps not so clear as Elves' memories. One of Earendil's earliest clear memories was of his mother singing over his cradle, when he was an infant, and he remembered her wearing the Elessar at the time. Significantly, he remembered that while still a mortal young man, sailing west trying to find his parents. Elrond and Elros might not remember their father, but they'll certainly remember their mother, and the attack.
That doesn't mean memories can't be distorted by fear and trauma, but I prefer them to know and remember the truth. I think it would make a more powerful story than letting the sons of Feanor take the easy way out of having to own up to what they did. I also want to avoid showing them lying to the twins. (It would also give us a chance to show them actually trying to make amends, which I think they did. Taking care of the twins was the last, or one of the last, good things they actually did in their lives, and I think it makes sense that it would push them to try to become somewhat better people. They can try to explain to children about the Oath and Illuvatar and the Void and so forth, but the simple mindset of children is sometimes a gift to see through excuses to the heart of the matter: they did evil things and have to admit it.)
We will also have to answer the question of why the twins don't run away. If I understand the Quenta passage correctly, they stayed with the Feanorians almost until the end of the First Age, well into adulthood. Initially the Feanorians take them back to Amon Ereb, but 2 years later Morgoth attacks and they all flee to the Isle of Balar. So now the Feanorians are on one side of the island, and everyone who survived the Havens is either on the other side, or leaves the Feanorian camp and goes over there ASAP. Why don't Elrond and Elros run away to the other side of the island? Or if they do run away (we can make a story about teenage runaways during the War of Wrath), why do they later go back to the Feanorians? Corey jokes about Elrond "growing up in captivity" and "Stockholm syndrome" but I don't want to show them being abused or kept as prisoners, and I don't think either is what Tolkien intended. If they find out the truth suddenly, after being lied to or misled for years, it seems to me they'd be more likely to run away permanently, than if they had already come to terms with what happened and the sons of Feanor had been honest and eventually earned reconciliation or forgiveness.
There's also the difficulty of hiding the truth from them, if any adults from the Havens ended up living among the Feanorians perforce. CRT introduced Cirdan and Gil-galad into the story as coming too late to save the Havens, and rescuing a lot of survivors. In the original texts where Cirdan doesn't exist, some or all of the survivors need to join the Feanorians because there's nowhere else to go. The Cirdan story is a good one and I think we should show him doing something, but I wonder... were the Falathrim able to get all the refugees away on their ships, even the severely wounded, and the missing? If anyone was left behind and survived, and didn't want to wander in the wilderness and get enslaved by Orcs... well they can try to cross the bay on a raft while still wounded, hide in the marsh hoping Cirdan's sailors return before they die of their wounds, or live with the Feanorians (and accept healing). Not a happy arrangement, and also not one that makes it easy to hide the truth from the twins.