When my daughter was born her older siblings gave her a build a bear bunny they created with a sound in they recorded saying hello/ welcome /we love you. I let them do the choosing and they loved it (2 and 3 at the time). Maybe you could do that and then go back and get him a matching big brother one? So they can exchange gifts and have a special same toy? You could record a special big brother message into his.
Dc2 due on the 23rd here so it's all going to get mixed up with Christmas (having our Christmas Day early too just in case I'm still in hospital after cs). The baby is getting DS (2.5) a big dinosaur he wouldn't put down (much tantrumming) the other day in JoJo. So I would say anything they are particularly 'into'. Congratulations! I'm starting to feel very nervous about having two to manage.