This has already been addressed in a similar post from someone else who was looking for a mod to enable children to cook just about any meal.
Carrigon has a couple mods using the toy oven to allow children to prepare and cook meals or prepare and cook pizza in the toy oven(s).
Check
this if you have OFB, HP and FFS installed.
If you only want a pizza-only toy oven, then
this will work for you. I've used this one before and have no problem with it.
If you have OFB through Seasons, then this
one will be more your forte.
All of these mods work with Apartment Life. Read and follow the directions to install and use the mod properly. You will have to register at Carrigon's site to download any of these mods. If you're interested in other food-related mods there, then this
section will do just that.
Forgot to mention that Mr Squinge doesn't do mods that involve adding animations to allow children to cook, or if other working mods are already in existence.