I know that Ubiquiti's Unifi line of products can do it. I only have their wireless access points. You can create user groups and assign connected clients to different user groups with certain bandwidth allowances. If I added a switch or the gateway, I would bet that it would work with wired connections as well.
But, getting into all of that stuff is pretty expensive from a consumer standpoint. If you only needed to limit wireless devices, you could buy a Ubiquiti wireless access point and do it that way (starts from ~$80 on Amazon Unifi UAP AC Lite).
Does your current router capable of having a guest network? If so, there may be a bandwidth limiting function for the guest network and have the tablets connect to that.
Also, sometimes these things require a static IP mapping for each device before you can set a bandwidth limitation in case the DHCP server assigns a different device the original IP address.