I reckon the .223 would be a good fit. As mentioned in the right hands a .223 will drop a pig, but the 22/250 won't hit pigs a whole lot harder (compared to a larger calibre). Same bullet, just going faster. Also, if you are shooting mostly foxes and the odd pig, .223 will be well suited, and it will be a bit more comfortable on the targets(noise, recoil,$$$). I've got a howa .223, and would buy another. Not sure if you are thinking along these lines, but don't buy a varmint barrelled gun. Good for what they're designed for and shooting out of cars, but a real chore to walk around with. And as mentioned, try and buy the best scope you can afford, as it can just go from rifle to rifle, but a nice .223 should be with him for a long time.
All the best.