It seems your T&C is fairly loaded meaning you have either a 3.8 or 4.0 liter V6. Both are rated for 16 city and 23 for highway mpg. While you are far off those numbers it isn’t that unusual to not get the epa mpg in real world driving. For instance if you idle the car to keep it warm or cold while waiting for the kids, or the school bus; running the motor when you aren’t moving kills gas mileage. If you live in an area with more than average hills, you’ll get less mpg. Oxygenated fuels (and ethanol) reduce mpg. If you live in Denver or a high altitude you’ll get less mpg.
The epa numbers allow you to compare vehicles, but they also create expectations that you’ll get those numbers in normal daily driving. In many cases the reality doesn’t meet that expectation. Make sure your tires are inflated the proper pressure. Have a mechanic check the brakes to be sure you don’t have a “dragging” brake. Keep the car tuned up with new plugs and air filter as per manufacturers recommendations.
Next time you need tires make sure you buy LRR (low rolling resistance) tires. On your van the tires can make a big difference in mpg. Michelin LRR tires can get you 5-10% better mpg than most standard radial tires. Other manufacturers of tires are also putting out very good LRR tires.