Dear Pupisek,
If I understood you right, then this can easily be done by brillkids
Just download (or create) the categories you want to show your child, then play them one after the other using playback. I think you can also create a playlist that plays all 5 categories consecutively and automatically
Watch the tutorial and try it ... you'll get a hang of it no worries
I was also wondering, if you replace the old categories as you were saying...does that mean that the old ones just get thrown out? or do you repeat again them after a while?
Hope this helps
Noha