I took your advice and just ordered (3) EAP245's - POE injector included for $90/each. I'd been looking at soho gear and had no idea business class stuff had become so affordable. I was browsing the TP-Link forums and also discovered that TP-Link just added mesh support for the EAP245 in a firmware release earlier this month. Being a managed device, I definitely think 802.11r/k/v will be the best option (or whatever TP-Link uses) over the mesh since I do have cabling where I need it.
I'm sure my wife and kids will be happier with our "production" wifi on the EAPs, since I won't really be messing with them after the initial setup. However I would still like to find a few devices that I can install openwrt on for lab/learning purposes. The TP-Link RE450 Extender appears to be supported by openwrt and it's my understanding has a Qualcomm chip. Can anyone recommend this device as something that supports openwrt and 802.11s?