The best way to use SPG points for travel is to transfer them to miles. When you choose to redeem points on the SPG website, there is an option to transfer them to miles. When you redeem 20,000 SPG points, you will receive 25,000 AA miles (it can take up to a week). Say you manage to earn 107,000 AA miles in each account by December 1st. You could transfer 13,000 SPG points to top off your AA account, then redeem 120,000 AA miles for one Anytime reward SEA-FCO.

You'll need to book one AA ticket from each account, select seats together, then call AA to link the reservations (just in case of later complications).

Do you have any SPG points now?