The normal practice is to measure such data at one or very few meaningful temperatures, where equilibria exist, then publish data extrapolated to room temperature, from which the user will extrapolate it again to the desired temperature. Formulas exist for the operations, they involve mainly the heat capacity, or better its integral.
The operation isn't completely trivial. It raises interrogations about its reliability, since errors occur frequently (mind the aggregation state!), and its accuracy because equilibria depend on exponentials of the data, while the proper data for extrapolation isn't always available. A heat capacity at flame temperature differs much from room temperature and is measured for few compounds - you're lucky with ethanol and ethylene. One must also use data that is meaningless, like the heat capacity of gaseous alumina or atomic hydrogen at room temperature, and amounts that may underflow or overflow a calculator.
So when you can use proven software to compute equilibria, it's safer, and much faster.
But sometimes, hand computations work.
Especially for the common compounds you mention, good data may well exist in the Janaf tables
, which are meant initially to compute equilibria in flames, more specifically in rocket engines. They are accurate, but use data formats less convenient for hand computations, with polynomials everywhere.
I'm not fully convinced that an equilibrium computation makes sense for butadiene at +400°C. I expect it to polymerize. Ethylene at low pressure maybe.