Both attractions should be open while you are there.
"Seasonally" means that they only open the attraction during peak crowd times (Summer, Christmas week, Easter and possibly spring break). Ordinarily this would mean you would be out of luck (you trip falls in a low attendance time), but, as you mentioned, they have decided to keep Timekeeper and CoP open year round until Stitch escape is completed.
The only seasonal attractions I know of that should be closed during your visit are all in Epcot in the Wonders of Life pavillion. They are Body Wars, Cranium Commando and The Making of Me. The entire Wonders of Life pavillion is now on a seasonal schedule, and since the above attractions are located in that pavillion, they will be closed during your trip.