No, there are no vehicles that fit six. Currently the max is five. You would need two cars in this instance, especially since you’ll have luggage, I assume.
You can get price ideas by downloading the Lyft app and pricing it different times of the day just don't order the car. it is also very possible one car will be more expensive than the other due to surge pricing as the prices do change and more so when there is multiple car requests in the same area if there are not a lot of cars.
with that said from what I saw of recent the prices were expensive and cheaper to pay for Mears.