Putting this out in the hopes that someone actually sees it and has some good ideas that could help formulate my plans of lashing this all together from a networking standpoint.

I have two Pis and an Arduino that I need to talk to eachother whilst having internet access, and just having one IP address to the network it's connecting to.

Primary thought is: Small TP link AP > ethernet switch > all Pis and Arduino. This would work, but it introduces another two devices to power in the form of the access point and the switch. Both could be ran from the Pi USB ports but I'd like them keeping to a minimum where possible.

Another thought could be to drop the switch and connect the AP to the Reaper Pi via ethernet, then have that Pi operate as an AP for the other devices on the board.

Then I would always have an established network on the board, and would just need to manage the AP for connecting with different WiFi networks.