What can I do to trick my 2.5-year-old toddler into walking longer distances?

Haha... I think there's no trick. You can promise to offer them a treat for covering so and so distance or playfully run after them or make them run after you... but I think all this for a little distance. For more physical activity, if there are kids his/her age then you can make them walk together. Kids are big copycats, they will walk just seeing each other, and you never know, this trick may work for longer distances as well. Else, be happy with whatever little walks your toddler does.