Definitely-- mini-vans. Have taken them several times. One adult can sit in front seat to allow more room in the back rows. There are usually a couple vans lined up with the Prius taxis. If not, they are around the corner and they just call one over for you. Just ask for "flat rate to DL". Same rate for Prius or van.
Something new (possibly): last weekend on Sunday the taxis were saying no flat rate return to airport due to demand. Usually Uber back to LGB is cheaper, but Uber was also at least double surge pricing. Have never not taken a flat rate back before. Our group took a towncar for $55 which is close to the flat rate anyways.