Ciao Kristineake and welcome to the forum!
There is a lot you can do, if you're not interested in Pisa and Florence that's super fine and gives you the chance to explore new areas off the usual routes. You could base yourself not far from the coast so that you can head to the beach for day outings but consider that the end of July is HIGH season for the beach, so if you want to stay anywhere there you have to already look into booking a place. Use this as a starting point:
https://www.tuscanyaccommodation.com/tuscany-seaside-accommodation/
You can base yourself in Maremma in souther Tuscany, further north in what is called the Etruscan Coast (which might be the better option considering the age of your kids) or even further north around the Versilia area - there is more of a nightlife in these last two if you base yourself in a town right on the coast.
Another alternative is to stay on Elba, which is magnificent but in July can get to feel crowded:
https://www.discovertuscany.com/elba/
More than anything, know that prices are the highest in this season along the coast.
You can also base yourself a bit inland, like in Volterra which is not a far drive straight west to the coast.
Or in Maremma inland, the same applies. In
Maremma you could spend a few days exploring: the hot springs at Saturnia, the towns of Pitigliano, Sovana and Sorano and the coast. You might also like going to see the
Tarot Sculpture outdoor garden near Capalbio.