Isabel, thank you for asking. We have been playing a photo game with local kids, called "Math Trek," where you go around and photograph particular math you find. Usually it's very hard to start finding, as you said, "multiplication in the park" - then kids find an example here and there - and then, wheeeeee! They fly and begin seeing multiplication again and again and again, everywhere, ten things per minute. Let's see if you and your crew can arrive at this happy place, or at least find a few examples of your own.
There are a lot of doubles in the park: spikes on symmetrical leaves (double each side), paws and toes of squirrels, legs of ants (3x2) and spiders (4x2). Many flowers have fixed number of petals, such as 5 on forget-me-nots; if there are ten flowers on the stem, that's 5x10.
Human-made structures in parks have multiplication, too. The sewer grill is often a grid with rows and columns of holes, say, recently we found 8x8 one with kids. Two wheels on a bike (count the spokes, times two) or four on a car or a stroller provide multiplication. A sidewalk with stones may be a grid.
Then there are microscopic structures with multiplications of large numbers - like parts of a spider web, or individual strands on either side of a feather, or a frond of a fern (look at dot patterns on the bottom side). Check out this beautiful video "Nature by numbers" for more inspiration. I am looking forward to pictures and stories of what you find!