Can I skateboard for Krishna?
There are two things going on here:
1. You like to skateboard.
2. You want to know: "Will it please Krishna if I skate?"
Answer: It depends. How can you know? Can you fly a plane for Krishna? Can you have a baby for Krishna? Can you make money for Krishna? Can you bake a pizza for Krishna? All these questions arise from one's material conditioning, a.k.a., psycho-physical nature. Pure devotional service is not based on material conditioning, but is the purest expression of one's very self. Srila Rupa Goswami tells us that pure devotional service is unmotivated (you don't want anything in return), uninterrupted (you don't do it only when it's convenient or you feel like it; neither is it impeded by any material cause), and favorable (Krishna has to be pleased by it).
The point of being a devotee is to do what is pleasing to Krishna. The only way to really be sure is to consult the spiritual master. If you don't have one, then you are left with figuring it out on your own, or asking on Facebook. If you get ten different answers here, how will you know which one is right?
If you decide that skating is too important to you to give up, regardless of whether you can "do it for Krishna," then it's evident that it's a material desire, although that doesn't make it evil. It's just what you do.
So how can you *make* it be pleasing to Krishna? By dovetailing it. That's where you have to get creative, consult with senior devotees, and commit to your chosen way, not giving it up because of inconveniences and obstacles. Otherwise, you're just indulging your whims. To be able to dovetail anything in the service of the Lord is a method for both the very neophyte and and the very advanced devotee. The neophyte is too attached to give up their particular object or activity, and the advanced devotee sees everything as Krishna's energy and uses it accordingly. Many, many problems in spiritual movements throughout history have resulted from people not being honest with themselves about which category they fall into. And don't be sentimental. Just because you say you're doing something for Krishna, or thinking of Him in a superficial way, doesn't make it service.
If skating is simply your desire, regulate the amount of time you skate and serve in other ways. But if you also feel like it's an authentic opportunity to give people Krishna, then think it through and develop a plan, and stick with the service until you break a leg or some better service comes your way.
"In the advanced stage of devotional service, the devotee does not see anything separate between his own interests and those of the Supreme Personality of Godhead. Both interests become one, for the devotee does not act for a separate interest. Whatever he does, he does in the interest of the Supreme Personality of Godhead. At that time he sees everything in the Supreme Personality of Godhead and the Supreme Personality of Godhead in everything. Having attained this stage of understanding, he sees no distinction between the spiritual and material worlds. In perfect vision, the material world becomes the spiritual world due to its being the external energy of the Supreme Lord. For the perfect devotee, the energy and the energetic are nondifferent. Thus the so-called material world becomes spiritual (sarvaṁ khalv idaṁ brahma). Everything is intended for the service of the Supreme Lord, and the expert devotee can utilize any so-called material thing for the Lord's service. One cannot serve the Lord without being situated on the spiritual platform. Thus if a so-called material thing is dovetailed in the service of the Lord, it is no longer to be considered material. Thus the pure devotee, in his perfect vision, sees from all angles."
You may not yet be a perfect devotee, but you can practice seeing everything, even skateboarding, as Krishna's energy, and act intelligently (with guidance when necessary) to figure out how to offer that particular energy to Him.