[TriLUG] Minecraft on Kubernetes with separate in home network help

[Matthew Glassman via TriLUG]

Hello group,

Here is the scenario and what I've got so far.  With a chance to learn and
the opportunity to provide my son with a Minecraft server, I decided to try
putting the item on Kubernetes.  I'm not there yet...   Here is what I have
which should suffice a Raspberry Pi and Router.   NOW here is where I am
currently stuck.

I have my ISP's router and a recently flashed old Cisco/Linksys router that
now has DD-WRT on it.  I want the latter router to create to be the router
on it's own network within my home network such that
1. Only certain items (the Minecraft items) can see this network outside of
administration.
2. Security settings to prevent or limit hacking attempts (IP range
blocking? Firewalls?)
3. Allows for particular users outside of network to get in in order to hit
the eventual minecraft server running on a raspberry pi.  I do not know if
that is handled at the router level or at the kubernetes nodeport level or
both.

I realize I probably could have created a VLAN on the ISP router and been
done with it but who said I do things the easy way ?     So I need some
guidance for a noob/novice.  What do you have for me?