Hi Katie, and welcome

I agree with you, I'd be wary too of cutting out too much of the diet of such a young child.....
The classic possible food triggers are dairy, and nightshade veggies, ie. tomatoes, eggplant and potatoes......
For me personally, citrus fruits and other acid foodstuffs trigger off my P as well.
So if you could find alternatives for some of the above, who knows, it might help.....
One thing that triggers off my P big time, is sugar..... and kids tend to get a lot of sugar in them these days - so maybe try to replace sweets with fruits, and soft drinks (both acid and sugar - very bad guys

) with fruit juices (melon juice is great, if you have a blender), or infusions.....
But no, I wouldn't make really drastic changes before seeing the GP - luckily march is not
that far off..... :-/

Good luck, let us know how it goes

Des