It's hard to choose one position, almost all imaginable are good, as people above have written (notice that almost all opinions are different and unique!). If I still have to choose one for each hole:
1) Mouth - bully (or rival, or friend and so on) sitting in armchair with legs spreaded, mom is kneeling on the floor between them with her head bobbing with wide amplitude up and down, up and down...
I look at this straight from mom's back or a little bit from backside
2) Pussy - Mating press, view straight from bully's back or a little bit from backside.
Mom laying on her back in the bed, her legs are up so high that her kneels are almost near her ears (and his legs spread in a way to support her raised legs with his arms going under her kneels in order to not her body to bent back horizontally).
If she is bare feet, her legs are bent in kneels over his arms in a way that I look straight at her feet from the left and right sides of bully.
If she wears shows or so, her legs in kneels are like 90 degrees so her very high heels look straight into ceiling.
Bully is jackhammering her deeply in mattress with whole length of his huge dick with fast speed (his big balls are slapping her pussy) and while his arms are supporting mom's legs, his hands are free to play with her big tits.
3) Anal - doggy style. View... actually from any side)
Mom is face low down, her big tits are pressed so tight that they show from the sides, her ass high up and bully is jackhammering her with whole length of his huge dick.
If he is kneeling behind her, her long hair wrapped around his one fist and he is pulling her by hair with thrusts, the other hand is giving hard slaps to both her cheeks: left, right, right, left..
If he is a little bit "standing over her" her hair will be wrapped around both of his fists, so he is "tightening the reins" while fucking her