1) Bathrooms - never too many.
This one is a no-brainer. Try sharing a bathroom with just one family is no picnic, but can you imagine getting a home for 4 adults and 4 children with only 2 bathrooms? Make sure you have enough bathrooms to allow everyone time to get ready to go out and have fun or the vacation could become a nightmare.
2) Space, space and more space.
Do not try to put two kids who each have their own room at your house into one room with a bunk bed. Believe me you will not be happy and neither will they.
Also make sure the kitchen is big enough and open enough to accommodate the number of guests. There is not much worse than having eight people in the kitchen trying to get something when the kitchen only can hold two. I recommend homes with kitchen islands so people do not have to go to the dining room to eat but can get a quick bite and go.
3) Creature comforts - Pool & Spa
Remember that you are on vacation. Nothing more relaxing that after going out for dinner then coming back to your vacation home and sitting in the hot tub. Believe me you will be thankful that you got it.
A pool can keep the kids busy for hours. If it is not summer time you may want to spring for the additional cost for heating the pool.
4) Asking the right questions.
Big mistake not to do some research and find out more about the place you are going to be spending your vacation. Read the reviews, then start asking questions that you found disconcerting in the reviews to ensure the problem was solved. Ask them how? Ask if they have a concierge service. Who should you call? Are they available 24/7?
When people leave their home for a long vacation all of the sudden their brain goes to into overdrive trying to think of every contingency plan and the items they can bring to solve it. Suddenly a vacation becomes more like survival camp. Pack what you need and enjoy your vacation instead of outlasting it.