Plan AheadBefore you arrive on their doorstep, let your relatives know that you're going to want to run during your stay. They'll appreciate the advance notice, and they can give you recommendations for when to run, so your runs won't interfere with family plans.
Find a Nearby GymIf weather or other conditions make it impossible to run outside, do your research and find a local gym that offers guest passes for a small fee. Also, check and see if your hometown gym has a branch in the city you're visiting.
Run Early in the MorningYou're less likely to disturb family plans if you run first thing in the morning, rather than trying to squeeze your run in sometime during the day. Try to get out the door before the rest of the house wakes up. You'll definitely win some brownie points with the in-laws if you return from your run with fresh bagels and coffee for everyone.
More: Tips for Running in the Morning
Ask Family Members to Join YouSee if anyone in the family wants to run with you. You may have to run a slower pace than you're used to, but use it as a recovery run. Even if no one else in the family runs, you can head to a local trail or track and see if anyone wants to walk while you run. You might be surprised to find out that other family members are looking for an excuse to get out of the house and be active. Going for a run or enjoying the outdoors together could be a great bonding experience.
Cut Back on Your MileageEven if you're close to your peak mileage for marathon training, you should have some rest weeks factored into your schedule. Use your family visiting time as an opportunity to give yourself a recovery week. You'll still be able to run and maintain your fitness, but you won't have to disappear for hours at a time to get a long run in.
Be Grateful for the New ExperienceI always love running on vacation or when visiting family because it gives me a chance to experience something different. Running in a new location will definitely improve your motivation to run while you're away. So, see it as an opportunity!
More: 7 Ways to Find Running Routes When You're Traveling