nah, you'll probably be pleasantly surprised how all of this goes down. They are far apart in age and an 8 year old is able to reason. You don't have to act like everything is about baby . . . as you'll be plenty busy with your 8 year old as well. This is the age where they dabble in multiple sports and activities. Get him involved in baseball, basketball, swim team, soccer, etc. Whatever he likes. Try putting him on some teams to see if you aren't sure. Kids try everything. Try boy scouts. Keep having his friends over for play dates, etc. Don't allow the baby to stop you from doing HIS things and he'll never resent the baby. He doesn't want to BE a baby. He just wants to be important and not get short changed on the kid stuff he needs to be doing because a baby is now on the scene. My sister's kids are this far apart. Baby went all sorts of places as my sister supported her older daughter and son. the older kids didn't miss things because baby needed to be home napping like she did with the first kids (had the luxury to do)--- baby learned to nap on the go! That third child of hers that is much younger than her other two is her best sleeper and most flexible child. :>)
At 8, he doesn't much care about baby clothes and diapers. He just wants to hang with his pals and know his life is not getting up ended. good luck
If he wants to feed, get diapers or wipes, let him. He would feel so proud that he gets to take that role. Let him pick clothes out for the baby or read a little story to have that sibling bond. Make sure you still have time for your regular routines if you have any with him. My daughter will be 4 and a half when I have my baby so getting her involved with doctor appointments, ultrasounds, picking clothes out for her brother. Your further along than I am but just the little things to make him feel he's still thought of. I'm 26 weeks 5 days