Hi Natasha,
It is hard to stick to a routine when there are outings and errands to be done. The best advice I can give is try and go out when it is activity time and not nap time. As they get older, they stay awake for longer and sleep a little less. This time won't last forever and your little one will be much happier when she gets her naps. As for your parents house, try to do a wind down routine similiar to the one you do at home, make sure the environment encourages sleep and just stick to it. My ds had problems sleeping at other people's houses for awhile, but as long as we stick to nap times, don't push him, and try to wind him down the same each time, he is getting better.
Hope this helps!