What we have done is to take the Space Bags along, but not pack any clothes in them for the trip out.
On the return trip, the dirty clothes go into the space bags, this frees up space for all the stuff we bought.
Is there a trick to keep everything from being wrinkled up?
I have the bags you roll to get the air out and haven't used them in years. I found them to be PITA as far as how much time it took me to pack.