I'm converting my 3700 sq foot home in the US to have something that supports seamless roaming and band steering. Currently I have the 3 Airport Extreme's on 1, 6, 11 for b/g/n, and 36, 132 (DFS?) and 149. The airport extremes have been rock solid - assuming you're somewhat nearby, however if you stray to edges of the home they don't swap back to b/g/n and drop WiFi calls. We also have a need for wifi in the back yard. 
 

Since the 225 doesn't support DFS I'm looking for recommendations on how to lay this out with 80MHz 5GHz channels. Comm closet is in the middle of the house on 1st floor (with 1 AP), office is on 2nd floor in front of home w/ one AP, and in back of home on 2nd floor is an AP over screen porch for back yard coverage. All areas have wired backhaul.   
 

Should I get at least 1 EAP245 as I (believe) they support DFS bands? Or just do 3 EAP245's and turn the 5ghz down or maybe setup front and back to share 5ghz channel and let channel in the middle of the home be on its own. Is it ok to overlap the 80MHz channels, or should I make them smaller?  I have 300 Mbps up/down fiber fiber and can consistently pull that much nearby the Airport extreme's.  I tried Unifi AC Pro's several years ago and they did not cooperate with some of my 802.11b/g devices (Harmony Hub was one, but there were several devices with issues).  They all went back.  I have one EAP225 now that I'm trying out. 
 

Any tips/tricks/advice would be appreciated.