I’d actually use a luxo iMac even today connected to the internet. IIRC it did have a firewall option. Of course any browser for PPC is going to be horribly out of date, but still its not going to get overwhelmed even directly plugging it in without a filtering router.
Also may I ask
- does that tablet get updates from the manufacturer/vendor
- is it as old as the last version of OSX that can run on that iMac?