I've been using LENSPENs with my DLSRs for years. They are great, however, they do use a small amount of charcoal to absorb moisture and oils, and sometimes there is a bit of dust left behind. I'd suggest getting a good puffer as well (puffer, not canned air), and blow everything clear after you clean the lens.
For what it's worth, LENSPEN also makes sensor cleaning pens (for cleaning DLSR sensors) that fit perfectly into the front obstacle avoidance lenses on the Mavic.
LP