I think you got some really great advice on here! My older yorkie gets annoyed with his little brother's playfulness and snaps violently at him (but has never hurt him). I hope everything works out for you! And if its your husband and daughters pushing to get rid of the bichons....Stand your ground! If it were me I'd would make them feel horrible about it....tell your daughters you can only keep 1 of them LOL
Maybe that will help them understand what they are really asking you to do....