Okay so. McG first- so in terms of knowing what Regulus really did already, I imagine that would depend on whether Harry's publicised it but just in terms of his school days- well, she has a grudge against the Slytherin Quidditch team but given that he was less trouble than his brother she's reasonably pleasant-neutral about him. Though he's always "Sirius's brother" in her head, lol.
And then Remus! Her fav of the Marauders! The responsible one! She's very fond of Remus (up to you if she knew his Big Furry Secret at Hogwarts but as his HoH I imagine she would have?) and will be pleased (for McGonagall) to see him alive again.
Next, Bella- dgaf about Remus, super easy. And then we've chatted Regulus and it's pretty much the same here, and she'll be pleased to see him because the presence of a ZILLION AURORS is making her twitchy. But she's a lot chiller (I mean, relative terms) with her wand in hand so at least she's not exploding all the time. Yet.