It is okay to only take a shower twice a week if you don't get really dirty or don't work outside the home.
However if you do work outside the home or go into public you should shower as you still may be producing body odor and others could smell it even if you don't smell it.
I wouldn't go longer than a few day to 3 days at most without showering and I would always shower everyday that I work or any day I go into public.
It's not bad to take a shower everyday if you really need to shower.
However if you don't need to shower everyday it's okay and actually good to skip a day of showering as showering too often can strip away the skins natural oils and could dry your skin out.
But if get dirty or sweaty and really do need to take a shower everyday then you should shower everyday.
I shower everyday when I work but will skip showering on the weekend unless I get really dirty and I've been just fine.
A person should shower at least as often as every few days if they don't get too dirty or don't work outside or sweat.
If you're sweating or getting dirty you should shower at least once or twice daily to stay clean but if you're not getting dirty or sweating you can go a few days or so without showering.
Even with kids they can go a few days without showering unless they get dirty or sweaty.
Kids should shower or bathe every 2 to 3 days unless they get dirty or sweaty sooner.
Kids need a bath or shower daily when they get sweaty or dirty or when they are going through puberty.
However kids that are not sweating or getting dirty only require a bath every 2 days or so or twice a week but if the kid is dirty or sweating or going through puberty and or has body odor they should bathe daily or shower daily.
Even adults that don't get dirty or sweaty can go a few days between bathing or showering.
However in the summer when you're sweating or the kid is sweating or getting dirty or if you work job such as outdoors where you get dirty then of course you should shower to clean off.
Although once a kid is going through puberty such as over 11 it's recommended that the kid bathes or showers daily as they can produce more body odor during puberty.
After puberty hits, daily showering is essential due to new hormones flowing through the body bringing along unwanted body odor and acne.
Your child should also wash their face twice a day with a gentle noncomedogenic face wash.