If you want to load balance the traffic on the isp side, you need to get with your providers on how to best achieve that. The issues there involve whether your org. owns a IANA assigned ip address space and maybe a BGP autonomous system id.
With the IPSec connections, you can tie hspr groups with ipsec crypto maps in ios 12.2t, and 12.3 code, but usually that is a failover, not a load balance mechanism. The idea of having one gre tunnel to one net on one router, and the other net on the other router will give you load-balancing, but not failover. Instead I would add ospf to the config and advertise the same nets to both routers, using different metrics. That will achive both your load balancing and failover goals. I would remove HSRP because all traffic will be directed to the active router; ospf and gre by themselves will accomplish your goals. HSRP can defeat them and it adds complexity to the mix.
I hope this helps.
