Plan to suit
I work from home at least 2-3 days a week and spend the rest at customers or out corporate office 100 miles away.
I have a wife that works part time and a 3 year old daughter who is at home all day 1.5 days per week (or all the time at the moment due to school holidays).
I find three main things help when dealing with distractions and this type of environment:
1. Set boundaries on when you can and can't be interrupted, although this can be difficult with Kids, but its easier with adults, try putting in noise cancelling headphones or similar and work in short 30 minute to 1 hour bursts taking natural breaks.
2. Go easy on yourself. Assuming that you have control over your time and are measured on results, plan tasks to take into account when people are not around to get the real focused work done, scheduling tasks which require less concentration when you are most likely to be disturbed.
3. Skew your work day and get up early or work late to get more undisturbed time to get work done while still having some time to enjoy the company of people that you are staying with or to explore where you are staying.