The Mazda5 is a good alternative for the minivan set - six seats and gas mileage 50% better than a full-size van; we consistently average 30 MPG with ours.

I think hybrids are a hideous con - the carbon footprint left by the much more complex manufacturing process can never be counterbalanced by any fuel savings, not to mention the heavy metals in those hundreds of thousands of enormous battery packs that are about to start reaching the end of their useful lives.    

It is also imprtant to realize how much plastic is involved in a New vehicle.   The Prius is no exception and is not the greenest solution for anyone looking for ecowheels.  Recycling older vehicles that get mid 20's in MPG is greener than the pollution from production of new cars.  Which is why Prii (plural prius) are more about "looking" eco concious than actually being green.  Buy a USED Diesel Jetta and produce your own bio if you really want green.

hate to be 'that guy', but in addition to surfing around for a new minivan, could you also lobby your local and state legislators to invest in public transit and bike lanes?

I know Los Angeles doesn't have the reputation of being the most pedestrian friendly city, but I hear your Bus system is actually pretty good. How about taking all of your passengers on the bus? It is definitely less convenient than shoving them on a minivan, but if they get used to transit at a young age, they are more likely to support it and use it as adults.... I know it worked for me.

In retirement we are considering downsizing to live in a travel trailer.  Are there any really green vehicles that can tow 7000-8000 lbs and cost under $40,000.

My 1999 Chrysler Minivan had a major tune-up last year (cost over $100) but is now getting 29 mpg on road trips where I control my speed to 55 mph.  I am getting 22 mpg in my stop-and-go city driving most of the time, but occasionally have a tankful where I only get 19 mpg in town; could be due to using the air conditioning this summer?

I am super concerned about MPG.
I mostly drive a 93 honda civicVX which gets
50MPG most of the time.
My business requires that I have room to carry sound equipment to a gig so rather than buy a van that get 10 MPG I bought a 2001 toyota rav4 standard shift and front wheel drive only.
I bought it used so I lucked out.
I get 30 MPG and thats the truth.  When I'm not carrying equipment and I'm easy on the gas pedal I can get 34/35MPG.
It is a good compromise and a nice car
Bill