Ttc with baby #2

My oldest is 2 and a half and me and him are the best of Friends, it was just me and him for a while and my boyfriend who I started officially dating a year and a half ago, my son loves him and he loves my son so much, we want 3/4 kids in total but we wants baby 2 soon and I’m all for it but I’m sooo scared my first is gonna feel left out of something :( he’s my baby n I just want him to have his siblings close with him but don’t want him feeling off