My Stepson

I'm 43M , My wife is 39 , She's slim with big tits and juicy ass . Her son is 17 now . Last night when we had sex naked , and when i drilled her holes from behind in doggy style, i found my stepson was watching us from window , it's little room in light. I think my wife forgot to close window yesterday. I saw that boy continued watched his mom's bouncing tits, I found my wife's son present still i didn't stop , i don't know why maybe i was about to cum . after 4-5 minutes, i cum in her small tiny pussy , she didn't even knew till now that her son sees us . Then she come over me and lick my dick . That time his son gone . I didn't told my wife that her son saw us had sex . Maybe I'm his second father that's why i didn't felt to stop. But i know my wife, she even never wear bikni in front of his son , she always dress up but now her own son see everything. Should i tell my wife?