I can tell you from my experience that the occasional wet night can continue for awhile being over tired or drinking a bit too much after supper or not making sure to pee before bed is all it takes to have a wet night.
You have been doing great Lucas and I would think if you try it without nappies on your own and wet the bed it will be much longer before your mum changes her mind.
If you use tape nappies you could leave the top tabs loose so your more comfortable but that would cause a leak if you do wet.
Do you think if you kept a journal on how many dry and wet nights you have if that might help to convince your mum your ready to go without a nappie?
With things improving so much for you it's understandable you want to sleep without a nappie so the next step should be to use just a mattress cover just in case you do wet.
It might take awhile to talk your mum into it but maybe with a journal and continued dry nights she will start letting you go without the nappie.
Our kids were switched a few years ago so it was when they were younger. If you decide to make the switch I would suggest before you do anything to sit down with your son and talk to him about what you are thinking of. At age 11 he should have input to this decision and after carefully explaining to him your side of things and your reasons for wanting to do so let him say what he has to say. Answer all the questions honestly. If after all this you both agree to trying them than it is necessary to get complete measurements of waist, hips, thighs and rise. In the case of plastic pants the waist and thigh measurements will be important when ordering them as they both need to fit snug but not to tight so as to cause red marks when he has them on.
I can offer more thoughts should you both agree to use them.
It's a tough situation for you diapering your younger sister.
For her to put on a cloth diaper by herself it would be very difficult and she most likely could not get it on right.
It sounds like when your parents are gone your the only option to diaper her.
You could have her apply the powder and rash cream herself if she uses it and have her put the diaper between her legs so she is covered up front.
It most be incredibly awkward for you but she can't help it that she wets the bed so maybe if she can do some of it on her own and at least have the diaper covering her privates that might help make it a little easier.
Unless she has a disability she should be able to do some things on her own and you can just do up the diaper pins making sure it's on right and she can put on the plastic pants when your done.
You could also talk to your parents about how uncomfortable this is for you and try to get them onboard with your sister doing when she can on her own and you just doing up the pins.
That may help you feel less awkward about it hopefully she grows out of bed wetting soon but until then it's understandable she needs help.
When our daughter started puberty past age 12,she also started bedwetting so we got her cloth diapers and plastic pants to wear to bed.At first she was pinning the diapers on her self,then would put the rubberpants on over them.Every so often,i would notice a small wet spot on her bedsheets and thought maybe the rubberpants leaked.A few nights after she was in bed and asleep,i checked on her and found part of her diapers were sticking out from the leg openings of the rubberpants! When she would put them on,she didnt make sure they covered her diapers.So i told her that i would put the diapers and rubberpants on her at bedtime.It became a nightly routine and now she is just past 15 and her bedwetting is starting to ease up,but i still put the diapers and rubberpants on her.