Valencia Solo with 2 Kids Question

I’m a mom from the US traveling to Valencia with my 2 kids- 3 and 5. My husband cannot join us so it’s just us three.

The kids will be in an immersion program during the day. I am keeping out itinerary very light and simple. Weekends will be in Valencia or short day trips in the surrounding area.

However! Seville has always been a dream to go. I would like this to be our one weekend excursion. Leave Friday morning, back Sunday night. Fast rail train 4.5 hours.

Is that doing too much? It would be the first weekend of July so planning for the heat (we come from a hot area so this is doable). I don’t want to over extend ourselves but also YOLO ?

Would feedback from folks that are familiar with these areas and distances! thanks!