I think, if you vaguely know him, I'd make the most of that and ask his opinion! He always has the option not to reply. It's always useful to know what someone else thinks of an agency - even though each person's experience with an agent is likely to differ: what works for one will not necessarily work for another.
I know that £25 isn't much, but I still think that's wrong. (Especially considering the much vaunted "ethical approach" on the website). However, I am well aware that my view is not shared by lots of people, so I'm not expecting you to share it necessarily either! The thing is,
it does not cost £25 to upload someone's photographs to a website, so they are making a profit out of this and there is absolutely no guarantee (of course) that any work will be forthcoming. I'm not sure how many they have on their books, but it does look as though it's several hundred, so that's thousands of pounds they have "earned" just for creating a website. Many/most of these people won't get any work (because there are not several hundred jobs available and of course this isn't the only agency touting for work for clients - there are hundreds and hundreds of agencies throughout the country).
In my opinion, an agent should earn money from commission, not from website creation. Of course Fresh Agents is by no means alone in using this business model and £25 is heck of a lot less than some other agents charge. Still think it's wrong though
I don't know much about children's agencies, but if you search round this site you will certainly find some names to try. You could also get hold of the book "Contacts" published by Spotlight and/or "Actors Year Book" which list agents. It's always difficult, recommending agencies, because what works for one doesn't necessarily work for another.
If your son is interested in acting more than modelling then I would recommend trying to find an agent with far fewer clients and one that concentrates on acting rather than extra and modelling work. If he want to try modelling, then perhaps £25 isn't too big a gamble. I don't know much about modelling to be honest, you many get much more helpful advice about that from others on this site.