-I ADORE my 2000 TDI Golf and recommend them highly. 47 mpg almost every tank, with a low at 42 when I towed 1000#'s for 500 miles, and 53mpg for the first two tanks (1300 miles) which were 90% highway. It sits 4-5, the seats fold flat (I have fit 3 55 gallon drums in it), has all the luxury amenities like butt warmers , great audio, and moonroofs, and it has enough power to pull 1500#'s in a 5x8 trailer up to 80 mph. $8k gets you a nice one and they last - mine has 140,000 miles with no rust (stainless exhaust) and another 100k in it.
This would be my recommendation (a Jetta Wagon is preferred - but they are more expensive and rare)
if you want to replace just the minivan and don't see the need for a larger vehicle (see below)
. If you are serious I can let you test drive it and answer any additional questions - they need new suspensions every 100k miles, but that is their only real weak point mechanically.
-** My favorite** For the $7-8k difference between selling your Civic and buying one of the above options you can buy (an have installed) an entire new motor, transmission, and have the entire body stripped, repaired and repainted. It likely still gets 35-40 mpg and converts easily to Ethanol ($300) should the need arise. There are lots of out of work or under employed mechanics out there (I can recommend a great one) that could use the money. $200 a month -every month- (unlikely) in repairs for the next 3 years would still leave you ahead of the game vs the above options. The 10 mg difference between the Civic and the Pruis is only about 120 gallons of gas for 20,000 miles - about .3 tons of C02 which is not that big an issue - plan a tree a year (3001 v. 3000) to offset it.
With unemployment on the rise I think the social justice aspect of keeping old cars running is an important consideration - both your cars are imports and designed to run 250k+ miles before a major system (cylinder head, block, or tranny) rebuild.
Larger Vehicle
-This may not be a comfortable subject, but it needs to be broached: it may be time for a Farm Truck. With 30 acres you will find yourself coming across weekly, and even daily, needs for a pickup or large trailer. Feed for the sheep will fit in the van, but what about 2 yards of soil amendments? 3000 willow rods? Lumber for a shed? If the tractor gets a flat how will you transport the tire? There are more than just "societal norm" reasons that every farm has a truck. A good used 90's 1/2 ton truck can be had for $4-6000 with either gas or diesel engines - the diesels will have ALOT more towing capability (10,000#'s+) but be on the high end of the price, are likely more truck than you need, and may need some luv. They will also get 20-22mpg vs 15-18. Greg's midsize Toyota is an awesome compromise, but make sure any truck can tow 5000#'s plus and hold 500#'s+ in the bed. Solid roof racks are hard to beat - giving you the option to move 16-20' sticks of timber, 24' ladders, etc.
--**Preferred** The only thing that a truck has over a good trailer is the ability to move ALOT of weight - your minivan can't really tow more than 3000#'s, where a truck could tow the entire tractor. If you think that is not needed - a trailer is very hard to beat. I run my entire farm and LLC operation off of a 5x8 trailer which can hold 1500#'s: which is 2 yards of manure, 3 yards of chips, or 3000 potatoes. A 5x10 should work on your minivan and provide alot of utility. My trailer was $700, a 5x10 can be found for $1300 -new- at Farm and Fleet. The best thing about trailers is that they can also be towed by your tractor into the field and when you remove it from your van, you go back to getting your 24-28mpg. $1300 is alot better then $6000 and the maintenance is close to zero. Trailers are also MUCH easier to load than trucks as the bed height is under 2' tall and you don't need to pay licensing or insurance on many of them.
Craigslist is FULL of options right now if you are game - deals are common as an unfortunate repercussion of the New Depression.
I know you said that you don't want to think new, but Subaru is bringing the Forester in with their new diesel in 2010. 37mpg, AWD, and it tows over 4000#'s. A true Jack of All Trades for $25k.
Good luck!
-Rob