3 yr old handling big changes

I've been fortunate at my previous job position to work 36-40 hours in three days every Friday Saturday sunday for years. I'd still see my two boys after work those days also, but more importantly be available to them monday through Thursday all day. My oldest son is now 13, my youngest however is three and a half. Some changes will be happening, I will be moving to a monday through Friday 9-5 or 8-4 position now. I just finished another degree and at the end of my program my schedule got busy as hell. I would have to leave during the week for school related things and my youngest.... it affected him. I'd start to leave and he would often get very upset. His behavior demonstrated him being distressed over me leaving more etc at that time. Him being angry and very emotional at home etc. Now I'm done I've been job searching and found a position. He is spoiled by having me home with him all week. He is very sweet, attached, loving, fun.... animated. It breaks MY heart.. the change... I'm used to being home all week with him. But I'm scared of how it's going to affect him. I got divorced last year... right now the schedule is that he has him weekends because I WAS working then so it worked out. When I start this new job... he will still have him weekends until I can get to court and have the schedule readjusted. So that will make it even harder for him. Seeing me that much less. What can I do? How much is this going to hurt or affect him. It IS a huge change for him. And I'm afraid.