To load balance on redundant links, you will need to coordinate this with your ISP. Because the settings need to match on both ends.
Make sure both sides have CEF enabled. In configuration mode, type: IP CEF. And use IP LOAD-SHARING PER-PACKET on every interface you need this done on. The settings should match on both routers.
If you are using voice or video, per-packet will not work, since there is not mechanism for out of sequence packets