Sorry for top posting.
Is it just one computer that needs redundant links? If so,
just having both up with wifi as a higher metric will work.
If its more than one computer across the bridge, you need
something at layer2 like STP or HSRP/VRRP
It would be a couple, all of those needing the redundancy are Linux
boxes, ranging from a Raspberry Pi to a netbook. Hmm, having both
interfaces up is probably not an option, thanks to NAT and the need
for port forwarding (wouldn't changing interfaces mean changing IPs?