Congrats on your new baby!! If you're looking for something that he'll look back on and think how special, then any of these other gift ideas sound perfect ( I wish I had known about them last year!!). But - if you're just looking for something to make him extremely happy in the moment, have the baby buy him whatever toy or theme he is into right now, and he'll be so excited that the baby already knows what he loves! My kids are 2.9 apart, and my son loves guitars but we hadn't gotten him one, so we had his baby brother buy him a guitar ( a toy one) and he couldn't believe his good fortune! That was a year and a half ago and it's still his favortie. It is a good idea to have something on hand that he loves as the baby will be getting so much attention and so many gifts from other people.
Good luck!