You are correct that HSRP & GLBP is for LAN only. You cannot use it in WAN. Therefore, you have to use routing protocol to provide the redundancy function. e.g. EIGRP, OSPF, equal cost static route, etc.
In your case, I believe there is routing protocol in place, you just need to enable or fine tune it as load-sharing is fine. However, you also need to consider the bandwidth of the uplinks from access to distribution, if they are not similiar but enabled w/ load-sharing, the traffic may be overloaded on the lower bandwidth link.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...