For non-critical, "fire and forget" messages, both IR and wireless will work. Both are pretty cheap.
I would probably want to do IR RC for a 'toy' because it also might be fun to use an existing, or low-cost IR remote control too.
That way you could also build a 'User Interface' to the toy which looks quite professional, is very cheap (£1) if that became interesting. Imagine, you could even trigger the toy using your TV remote or something. (IR remotes are one of the cheapest, and most flexible ways to make a reasonable looking user interface to small projects)
IR can be done for about £1 for each end of a one way communication.
If you want to learn about it, it'd further justify using IR. It is pretty interesting, and is relatively easy to understand, so that you could even make it from raw components if that became interesting. It works reliably for, probably, billions of consumer products.
IR generates very little "communication pollution". It is extremely unlikely that an IR system would have any impact on a neighbour. Wireless isn't quite as well behaved. Clumsily implemented wireless communication in the same vicinity could interfere with one another.
There are web sites offering complete Arduino code, and advice on how to build and test IR remote control. For example IR and "Ken Shirriff
