Personally, I wouldn't make a habit of offering alternatives - it can become a bit of a trap, particularly if you have a fussy eater. I made that mistake & learnt the hard way its not a good idea! That said, if he was teething/off colour I probably would offer him something else a little later, but try & make it separate from dinner time, so he doesn't think if he refuses his dinner he will get XYZ. When offering a new food, it can be a good idea to serve it alongside something you know he likes, so there is still something else he can eat if he's not so keen on the new food, yk?