Traveling from Santo Domingo to Punta Cana

Hola...Hello. I'm preparing a trip for 4 of us in August to DR. We'll stay a couple of nights in SD and then we're headed to Punta Cana.

I need information on private transportation (or taxi) that can take all of us from SD to Punta Cana... and then a couple of days later do the return trip since all our flights will be from SD.

Can I get a taxi to do this? How much would it cost? Would the four of us be comfortable during the long ride?

Are there any other options besides taxis? I know there's the Express Bavaro, which I may do, but there's one person traveling with us who would rather go by other means.

Thanks in advance.

This is the best information that I've read on this forum:

traveling within dr - DR1 Dominican Republic Forums

I will do option 1 and take the Expresso Bavaro, we'll just have to be there early enough to secure seats. DR 250 pesos (assuming this is still current) is about $7 or $8 depending on exchange rate, so this is quite affordable and the buses seem quite comfortable. We'll be in SD for a couple of days before we head to PC, so we'll be checking it all out first.