If we're still around - in whatever form - then the easiest solution will be to change the planet's albedo. If we can do so via bioengineered means, then all well and good. Increasing the planet's cloud cover is one approach - Venus, today, could be kept in a habitable state if its sub-solar point was suitably reflective and it retained its water. Ironically, if tide-locked, there would never have been a runaway greenhouse, so that might be the solution for Earth in the end. Alternatively putting most of the water underground means it can remain stable up to an insolation of 1.7 times the present. Since we want to move it outwards a bit anyway, then shifting to ~1.16 AU means it will fine when the Sun hits the Redwards traverse and shines at ~2.3 times its present output for another ~0.9 Gyr after the Main Sequence ends at 5.5 Gyr from now.

No one thinks BIG enough nor small enough. Push Earth slowly out from the Sun and the required thrust is pretty low - if sustained for ~6 Gyr.