Migrate from Aperture to iPhoto

If you have iPhoto 11 v9.4.3 then you can just open the Aperture Library with iPhoto. Job done. If you don't then you're out of luck. There is no migration path.

There is no reason to assume that iPhoto will be supported any longer than Aperture. As you're on 10.8 both apps will continue to run anyway.

There is a 21.5" iMac.

And that Photos will probably be better than iPhoto, but a bit less than Aperture.

I am not planning to update my iMac yet (hoping for a smaller size than 27" as we don't have the desk space much as I would love the big screen) but would like to get my photos out of Aperture and into iPhoto as I imagine iPhoto will be supported for longer than Aperture.

Both iPhoto and Aperture are being discontinued, so converting to iPhoto will not change much. (Aperture is Dead. Long Live Photos! | ApertureExpert). The new Photos.app for mac will be the successor to both Aperture and iPhoto.

But to migrate from Aperture to iPhoto: With Aperture 3.4.5 you should be able to open your Aperture libraries in iPhoto 9.4.5. straight away.

Which iPhoto version do you have? Since Aperture 3.3. and iPhoto 9.3 are both applications using the same photo library. You can switch freely between them. Have a look at this support document: Aperture 3.3: Using a unified photo library with iPhoto and Aperture