[2020] Is it possible to skip and do the side missions later (kenley college, coney island) after you finish WONY?

I just recently played the Division 2 and played it from level 1-30 and got to World Tier 5 (didn't use the boost) but didn't do any of the Side Missions yet, like Kenley College and Coney Island... I'm aware that once you go to NY, you have to finish it before you can go back to DC... My question is, would I still have the opportunity to do these missions after I get to level 40 and finish WONY or do I have to do them now? And what happens to my unspent SHDs when I get to NY? Thanks for the answers.