Are the batteries removable and if so, how much do the bikes weigh without the batteries? That is going to be key to determining what bike rack may work. You will probably find that many bike racks are limited to 50lbs per bike and a few are 60.
Our electric bikes are about 62lbs each with the battery (50 without) and we have not found a bike rack yet that is a good match. However, ours are also folding bikes and when we travel we take the batteries out, fold them up, and put them in the back of our toad. That actually works better than the rack as it keeps them out of bad weather is more secure while traveling. We are still looking for a rack as we do have a hitch on the back of our CRV and would like the convenience of using the rack if we are at home and want to go somewhere for a quick ride.