Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
AA only offers one-way awards. I'm not sure if UA offers a RTW award, but frankly, the OP might be better off just using his miles for a series of one-way, long-distance flights, and use LCCs for local travel within each region.
There are no surcharges when redeeming UA miles on any carrier. There are no surcharges when redeeming AA miles on any carrier except BA and IB.