Unless the wheels that came with that tandem are tubeless ready (unlikely) you are going to need completely new wheels to go tubeless. $$$. Then you will need new tires. More $$$. You need new tires anyway, clearly your present ones don't have enough flat-proofing for your conditions. Marathon Plus are the go to choice for this kind of assignment. Conti GatorSkins are another. It is not a binary 'tubeless = no flats/ regular tires = flats' kind of equation. There are flat proof and flat resistant tires that will mount right onto your present rims and do a great job. I doubt a pair of MP's will cost more than new wheels, tires, sealant, and etc. to go tubeless. You have e-assist. That means putting Slime in your present tires need not be a ride pleasure killing action like it might be if you actually had to push around the stuff with your own energy. "Friends don't let friends go tubeless" -Leisesturm