Although these websites I have recommended are for children I would definitely advise that you supervise the use of them (or certainly have your 'eye' on the screen while the children are using it). It may be that some websites provide links to other websites which are not suitable. I would also advise extreme caution when allowing children to look for animal videos on Youtube. There are lots of wonderful Youtube channels out there but be aware that a quick search for information on say, scorpions, can quickly offer up unsavoury videos which could be distressing for children to watch (eg. 'scorpion verses gecko fight' or some other cruelty).
IUCN Red List The official list of endangered species, it takes time to navigate but I find it fascinating. https://www.iucnredlist.org/about/background-history