Warren opted to come with us, but was nearly certain she meant Lexington Park. When we ended up following Margaret's directions north on Packard instead of south he clearly started to question whether there was a park to be had at the end of the trip or not. He asked Margaret, "Is it near the bike path?" She answered yes rather uncertainly but continued to assert that north on Packard was correct. Warren bailed two-thirds of the way up the big hill that Tufts is on since I was insisting of following Dear Leader's directions.
Sure enough, we eventually got to a park, pretty much as described. There were no dedicated sand boxes, though some of the play structures were in sand, there was a basketball court, the color scheme was reddish-orange and brown, and assuming that Hongmei ended up taking the same route home I did down route 16 it totally made sense that she would take them there prior to stopping at Foodmaster for groceries. (It's not really on the way to Foodmaster, but the store is just off that route back.)
We ended up spending all of ten minutes at the park (Margaret had the sudden urge to poop), but the moral of the story is that if you're willing to trust your preschooler's directions you may be rewarded. Of course the other possible moral is that if you are willing to go on walks of unknown direction, difficulty and duration while pushing a heavily laden double stroller and while 37 weeks pregnant and feeling an annoying amount of pubic bone pain it is just remotely possible that you indulge your preschooler too much. Maybe.
(Looking it up on google maps, the park in question seems to be at roughly 137 Capen Street in Medford.)