If you wanted to send traffic over both links you would need to use the variance command under the EIGRP PROCESS
what the VARIENCE does under EIGRP Process?
Okay firstly you need to obtain the metric for the L3 etherchannel route. You can get this from the routing table -
"sh ip route x.x.x.x x.x.x.x".
Find the route entry and the second figure in the square brackets so it should be [90/xxxxxx]. You are interested in the xxxxxx figure.
Secondly you need to see if the second connection is in the EIGRP topology table because if it isn't it will need to be and you may to manipulate the metrics to get it there.
"sh ip eigrp topology" will show you the EIGRP topology table. If the route via the 300M link is in there note down the metric.
Next you need to work out how many times you need to multiply the metric of the best route to get to the metric of the 300m link. This is your variance figure.
If the route for the 300M link is not in the EIGRP topology table you will need to adjust the metrics to get it there. See Narayan's post from previous EIGRP discussion on what you need to do.