Seconding BGP between the concentrators and your core(s)! We have a very similar setup - 2 DC's each with 2 hubs (each hub on a different ISP), DC's connected via dark fiber, with ~200 spoke sites participating in the AutoVPN. All the spokes are full-tunnel AutoVPN.
We have BGP stood up between the concentrators and the core L3 switches at both DC's, with the core L3 switches advertising their local supernet into the AutoVPN and receiving routes to the spokes from the AutoVPN. The BGP routes are redistributed into EIGRP, and the core L3 switch at both DC's share routes with eachother via EIGRP. We control/massage load by adjusting the hub priority on a per-site basis to spread the love between both datacenters (and between the concentrators/ISP's at those datacenters).
Prior to standing up BGP between the concentrators and the core switches, we were using OSFP and the 'local networks' to advertise the DC supernets into the AutoVPN. However, in this setup, if we lost one or both of the concentrators at one DC, the routes through that VPN concentrator never dropped out of AutoVPN and caused a black-hole situation. This may have been a configuration issue on our side, not sure.
One gotcha I remember having to chase up was getting Meraki support to stop the hubs from routing between eachother over the AutoVPN (instead of dumping traffic to the L3 core and letting it route across the dark fiber).