To an earlier mention of Minsc, who is our big n strong but not bright, beloved ranger, doesn't he hate Vampires so would he hate Astarion and have a similar dynamic that Shadowheart and Laezel have where the two hate whatever makes the other happy?
If I remember it correctly, in BG1 he had Gnolls as favoured enemy, and in BG2 he had Vampires. His reasons for that are long past, but he should still be quite unwelcoming of a Vampire in the party. If Astarion explains to Minsc that Vampire spawns are miniature Vampires not at all from the giant space, and thus not a danger, it may fly.
Dumb half joke for them to be more friendly: Astarion seemingly out of character treats Boo really really nicely because he is actually a nice guy who likes hamsters and the two bond and become best buds (In minsc's eyes. In reality astarion was debating eating the little guy as a snack but now hes stuck hugged by the big brute and having to play it off.)
