is it possible to go from a 2.5 to a new caravan 3.8 or am I just dreaming, I don't know much these engine swap options.

Money and time make everything possible.  I'd start by pulling your engine out and seeing if a friend would let you "borrow" the van to look at the swap.  Pulling the motor shouldn't be too bad on the van, so you can pull it, leave it on the hoist, and lower it to judge clearance issues.

Ill give you some basics of what your up against...the computor that runs the 3.8 is different
than the 2 .5, the 3.8 only has one transmission that bolts to it,, 604 overdrive, run by a
on board computor.. however the 3.0 engine has a option on a transmission being the
604 and the470 that is throttle operated not computor operated...However the 3.0
also had a different computor from 3.8 and 2.5,, If you want a mini with a 3.8
I
suggest go  buy one.. Im looking myself at the possibility of putting a 3.8 in a dodge
spirit equiped with the 3.0  and 604 overdrive, the key is either putting a3.8
computor system to run the engine or convert to a aftermarket carb or throttle
body and use a 6 AL box to make a a new ignition..Thats my thoughts on your idea
Roger Reynolds  Hannibal trans mission and 604 quick change gears.

stick to the 3.0, or the daring task of shoe horning the 3.5.

The computer system on the new eclipse 3.8l is different too (I believe). So unless you have the time, money, and know how, I wouldnt suggest even researching the idea.