Travel time Dzibuchaltun to Merida to Progreso

We are considering doing the Autoprogreso tour of Dzibuchaltun and Merida in February. We will have our almost 5 year old with us who is used to traveling but we're trying to figure out the transit times. Does anyone know how long the bus from Dzibuchaltun to Merida is and Merida back to Progreso? Is the Autoprogreso tour in Merida walking or on the bus the whole time?

Thanks

I have not been myself but we met some people that did and they had two pre-school children age 3 & 4 and I believe she said that it was just under 3 hours. I do remember that she said that if they ever went again she would dress the kids in jeans instead of shorts (that's just what she said...don't know why). The trip is there is very short and I seem to remember 25 min. each way.