You don't need your phone at the playground
I took my kids to the playground a few weeks ago, and decided to leave my phone in my purse, as much as I could. I took it out for a few pictures, so their daddy could have a glimpse into our day, but other than that I made sure to put it back up. I wanted to be present. See them play, be able to fully devote myself to pushing them on the swing, marveling at how fast they went down the slides, and how high they can jump off the rocks
We had a good afternoon. They Loved it! They kept mentioning how much fun I was to play with...even though I kept my shenanigans to swing pushing and shouting "AWESOME!" at all their cool jumps.
You know what though, it was fun that day. They didn't see me devoted to my phone on a bench, they saw me devoted to them, standing beside or behind them as I pushed the swing or encouraged them to pump their legs. They saw me sitting on the bench waving at them randomly to acknowledge that I was watching them (and sometimes in an attempt to embarrass them). They heard me encourage them...a few times they heard me correcting them (slides are for going down on not UP).
I get it though too...Sometimes you take your kids to the park for a break. TRUST ME, I understand. Maybe instead of being on your phone, soak up the sun, take in the blue sky, breathe in the air, or read a book. Maybe sit on the bench, and just "be" for a bit. Because you do need a break.
Don't let your phone become the thing you are most concerned with. Because they (your children) will see how much value you place upon it. They will think it has more value than them.
Instead just leave it. Either in your purse, diaper bag, car or at home (Although it is a useful tool for in case of an emergency). Let yourself be available and present. I think you may find you will have fun too...and maybe even a little sunburn.