You can do that.. but it would be best to tuck them in once hatch is complete... I think. The adoptees will be fully mobile while the new hatchers will still be trying to get their land legs.
If you can't have roos... I would not hatch. However, I would take my chances with sexed pullets in a breed I like over sex links which are notorious for reproductive cancer type stuff and often passing by two years old.
I ONLY have that issue if waiting until the chicks are too old.
ETA: I would NOT want to be on vacation during hatch... so many things can happen... And I want to know WHAT happened... for example if all the chicks die was it a terrible mum or flock antics, simple failure to thrive, rats... what???