My husband and I are moving into our first home on June 1st.
We are bringing with us our two inside cats that we've had for over 6 years.
I know cats are not fans of change or new places. I know that we need to limit them to one room the first day and make sure they know where everything is. We are moving from about 1200sq feet to nearly 5000sq feet (including a finished basement.)
The problem is that we move on June 1st and on June 8th we are going on a week long vacation without the cats that we've had planned for over a year. We are moving in about 3 weeks later than we had hoped so we could avoid this happening. I've bought them each a cat bed so it'll have a familiar scent (which they have no interest in) and also cat pheromones which also don't seem the phase them.
They already don't like when we go on vacation. One is super clingy and needy when we get home and the other is mad and won't come near me for a few hours. One is 4 years old and the other is maybe 8. Both in good health.
I've read horror stories about cats not transitioning well and inappropriately marking, stopping their grooming, biting their tails, etc.
Any tips for making sure their transition is a good one? Advice? Am I overly concerned?

Don't worry about it because cats bounce back, the timing depends on the cat. Rarely, a cat may mark, but that will be due to stress or the cat being territorial in a new place. However, if they are house-trained it will only be temporary (if it happens).

(First house, brand new carpet... thanks, boys!)