Re: GB games still working?
Average life of the battery's something like 10-15 years. So it's unfortunate, but you won't be able to show your child anything if it's like 10-15 years into the future. The GS ones die faster because it keeps track of time as well.
AFAIK, all pokemon games suffer from this plague sooner or later. DPPBW era games you can make a back-up save by exporting the save out via action replay. That would be a permanent save in that sense, since it'll be ported to a more durable hard drive.