Yes, you can recharge your 2017 MacBook Pro with the PowerCore+ 26800 with Power Delivery. Keep in mind, however, that it will not charge at full speed. This charger would charge a 12" 2017 MacBook at full speed, and all iPads at full speed, but not MacBook Pros. Again, though, even with that being said, it will still charge it, just not as fast if you used a 61 W charger.
*Disclaimer: I do not have either device so I cannot say from experience.
Although Anker currently does not offer a portable charger that will charge your laptop at full speed, it may in the future. Stay tuned!