The contractor should do with the excavation material whatever you want, within the confines of what your building permit allows...

This is what our builder did, leveled off the yard as much as possible with the excavated dirt.

We have pretty much the same size lot and after excavation we have a really flat front yard, sloped side yards, and flat backyard. Our builder brought in extra dirt already and we're only just finishing framing so don't have a finish grade yet so it should get even better but we're really happy with it so far. Our last house had steeper front yard and side yard to get the walkout but the lot was only 1/4 acre so there is more room for things to leveled off with this lot,

Whether there will be enough or too much soil to do what you want also depends on how much slope the lot has.

I would assume it's possible to bring in additional if there's not enough soil based on the grade of the lot.

I would assume it's possible to bring in additional if there's not enough soil based on the grade of the lot.

Building up the grade of the property only works if the building dept allows it as you could be causing major runoff problems for neighbors or the streets in general. Check that out first as well.