I thought Etherchannel used Port aggregation protocol to dynamically enable channels. Anyway, I would never recommend turning off spannning tree.
Also, the 2948G-L3 sees every port as a routed interface. Did you set up a bridge group (I think that's what they're called) so that both ports on the L3 switch are in the same VLAN? If not, I doubt that Etherchannel will work.