Do you know the height of your vehicle?
Pay attention to the height of your camper van, as you'll be driving through LOTS of tunnels (especially on Senja). The lower profile vehicle you can get, the better.
There's one tunnel leading into central Tromsø that you need to avoid if you have any sort of camper, since you risk crashing into the top of the tunnel. Ask your camper van company which tunnels to be aware of before you start your roadtrip from Tromsø.
Also, roads can in Lofoten can be very narrow—especially if you're in a camper van-so just look far ahead and utilize turnouts, so you don't get in a situation where you're needing to reverse.