Maybe reset your expectations a bit, and just go out alone or with younger DC
I used to go swimming with DSs, we had not been for a year or two and I absentmindedly asked if they fancied to come along (they are 14 and 16), the look of horror on their faces was so funny
..."ehmmm, no offense mum, but going swimming with your mum at 14 is.. kinda weird"
As is walking around aimlessly in the park.... with your mum
Sometimes you just forget how quickly they are changing at this age
I do strike deals with them about walking the dog, but there is a purpose to that (dog needs walk). If you tell your DS you have to all go out now, but you are not even sure where, no wonder he gets stroppy as it's random and pointless.
Do you and DH have a tech free day as well by the way?
Teens hate random, pointless, unfair situations more than anything.
Ask him what he thinks would be fair, talk to him and with him instead of laying down rules. I find parenting changes a lot with teens, and mine respond much better to "the dog will need to walk this pm, can you walk her? Any time before 6?" Than "right. You need to come for a walk now"
Do talk to.him about bad behaviour/reactions though as obv that is not on
But seriously, walking in the park with mother...is not what teenagers love 