Most likely they are in the shallow water to eat algae that grows there. Depending on many things, algae will grow better where there is plenty, but not too much sunlight in the water. Algae will grow on the dead leaves and the tadpoles will graze them off. Some tadpoles eat other things. The big bullfrog tadpoles will eat each other.
I would suspect that they will be toads but it is hard to tell. Asking two engineers a biology question is asking for a bad answer.
Here is an Identification chart that I checked to be sure I at least had a few functioning brain cells left. Black ones are toads.
Tadpole Identification Table
I grew up catching and playing with toads and frogs and have a fondness for them (also crawfish and salamanders and ring necked snakes). When you grow up poor on a farm you don't have so many toys and the small creatures are your entertainment. Frogs and toads have been having a hard time the last decade of so probably because of acid rain and pH changes but the last I knew it was still an unsolved mystery.
You should be happy to have so many as they will eat lots and lots of bugs. The little ones will be a major food source for a lot of birds and shrews etc.
If you have children of an age to need a science fair project for next year there are some great ones, such as what percentage get rear legs on the same day, and front legs and leave the pond etc. Also is the question of how many are deformed and what kind of deformity- this should win if done well and advance your child to the regionals. Make sure to check the rules as working with live animals requires prior approval and not every school will allow project work done before the project is registered.