18,18,25.
but I'm sure the right clothes and behaviour will make 'mom' 40-ish. it's tough to pull 'old' look in bikinis in DAZ without making them hideous.
personally I go for as old as possible while still looking pretty (25-28 DAZ), then fake the rest with added body fat, wider hips, non-young hair, mature dialogue and behaviour. also by contrasting the younger characters especially with dialogue and behaviour. (avoid fancy words, avoid self-reflection, make young people a bit selfish. while older characters are more conservative, contemplative, make less grammar errors etc.)
about the punchable face...sadly there's no winning with male faces in DAZ. no man will ever look unpunchable, but you can fix that in writing.
for what it's worth, this dude is probably one of the least punchable looking DAZ males I've seen. so I wouldn't worry that much. it's not a fight you can ever win in the current state of DAZ.