The little tikes peak and rail set would be absolutely ideal for a 2.5 y/old boy.
We've got this set and a 2 year old who loves anything with wheels - he plays with it a lot.
P.S. You can usually pick them up very cheaply on ebay in good condition and with original boxes so if you don't mind second hand you can save a lot of dosh. At that age they won't know it's not brand spanking new.
Have just trawled ebay and although they are cheap as chips for the set itself, postage is about £10.00.
If you search by putting your postcode in and see if there are any within collection distance and keep doing this I'll bet you get one for a few quid in plenty of time before Christmas.
There always seem to be about a dozen of them for sale at any point in time and my skint friend got a perfect one for a winning bid of only 99p after a month or so by searching in this way and collecting it herself.
Many people sell them with things missing/replacement cars/figures substituted though so look at the descriptions carefully.