We have two boys, 4 and 2, and a newborn, and we love our Joovy Caboose stroller. We're on the trails a lot too and this has worked out great for us. The seat area in front is great for them to sit in, but the infant seat also can attach. The back "caboose" area allows them to either sit or stand, and we've found that we can even have all three kids ride by having one boy stand on the footstand in back while the other sits on the seat in back. It allows them to climb on and off by themselves, which is great for those who like to walk for awhile but then need a break. It has a snack tray, and for about $20 we bought a set that snaps on that includes a water bottle holder, cup holder, two snack cups, and a net for storage. There is also some storage under the back seat area.
I have also found that doing a sort of a scavenger hunt with our kids helps pass the time. We look for flowers of different colors and will let them pick a petal or two to sniff when they find one, we look for butterflies, birds, berries, pinecones, etc. They seem to like it. We also sometimes find an open area along the trail where they can get out and race. They do a couple races along a straight grassy stretch and then climb back on for a "rest" and drink of water.