Pod kits are probably the best "catch all" solution for older folks, but I'd even try handing your tank to your mum and asking her to refill it. If she can handle it ok then the choices widen. Sadly lot of tanks do sometimes get very difficult to take apart to refill, but most of the top fill ones are pretty good. The aio coil/tank based kits are good, but a lot of the time replacing the coil can take a bit of faffing - pushing the coil in while turning etc - and even filling them you have to be observant of the line. Some older folk might struggle with this, but again, I'm sure there are plenty who could cope ok so it's worth getting her to see how well she could cope with refilling etc.