there is only one computer i would recommend of the G4 G5 range , highly recommend really and its the eMac , but the 1.42 ghz model only , , even its only a G4 it is in reality not much slower then a iMac G5 1.8 and outperforms a mini g4 1.5 /ibook g4 1.42 due to better graphiccard and double the ram and faster harddrive ,
and is usually cheaper then a mini G4 , so you could get 3 of them for far less then 500 , they can play flash games (i did play a couple games that are on facebook ) and i had no problem at all to play online video at youtube or others up to 320p some even up to 480p ,
and if i look at the age of your kids , they wont need newest software at all within the next years anyway , i mean office 2004 still does the job and updates are still available today like the xml converter for the new file names with the x at the end like ppsx/docx which will enable to open files made by much newer office versions
another important bit to consider is the reliability , i vouch for the eMac 1.42 ,
but ibook's like to break down due to logicboard failures,dead or not charging batteries ,graphic card problems and people ask even with the defects double what a eMac would cost
and the iMac G5's like to blow capacitors and later get stripes on display ,
and with like i mean it is more likely to happen then not,
so to both if you dont just want iBook or iMac g5 for display purpose as a collector or if you are not a good solderer then hands away and dont think about it in your wildest dreams, no rule without exeption if the previous owner did a good and quality refurbishment , then yes get one , but it will cost you a lot to find that example