H.D.
It sounds as though your son is moving away from his naps, which can be a short or lengthy process, depending on what's going on in his life. (Children entering preschool and kindergarten may take naps for a while, esp. if they're tired...)
If it were me, I'd invite the older one to play quietly in the living room while I put the baby to sleep in the room. Then, I'd offer a half-hour of stories and then see where he was at. If he seemed tired, I'd try for a nap on the couch, if not, I'd offer some quiet play while I took care of what I needed to do. One way to do this is to set a timer and ask the child to sit and look at books, color or use playdough--whatever they enjoy doing-- independently until the timer went off. And then, after that time goes off, immediately come back and be ready to spend time with them. That part is really important and will reinforce this pattern to them. (the child learns "I am quiet and by myself and when the timer goes ding, mama always spends time with me")-- we must be consistent.
I'd also recommend starting a timer for no longer than 15 minutes at first, and then lengthening the time as your son gets used to being "on his own" during that time. He needs to know that the timer WILL eventually go off. 15 minutes is barely a tick to us, but an incredibly long time for a 30 month old wanting mom's attention. If you are in a bind, a quiet video might work as well. I'm not big on recommending tv, but heck, we all need a break!
Good luck! Just get into a consistent routine, and with time he will be able to anticipate and expect what's going to happen around rest time.