Looks like a great idea, but I would shut both off if leaving the house overnight. A great company that supplies these fittings is here: BrassCraft - 2 faucet valves

thanks so much! Yes I will be careful with that but thanks for tip. And my solar pump shuts off automatically with low water..

Creative thinking, I like that. The only thing I would add to your setup is a vacuum breaker such as this:

https://www.homedepot.com/p/Everbilt-3-4-in-Hose-Bibb-Vacuum-Breaker-VACBFPZ4EB/205815672

Plumbing codes require and air breaker whenever dealing with a potable drinking water supply which could be connected to a non-potable water source (which I presume your garden fountain would be!). The thinking is that if the house water supply ever fails and develops a suction, the non-potable water could be pulled into and contaminate the potable house water. Not good. The vacuum breaker prevents this situation from ever happening, it's cheap insurance. Install the breaker between the timer outlet and the line going to the fountain. The hose bib timer I'm envisioning is those that might be battery operated and used for small drip irrigation setups, like this:.

https://www.amazon.com/Orbit-62061Z-Single-Programmable-1-Valve/dp/B004INGS8S/ref=zg_bs_553988_1?_encoding=UTF8&psc=1&refRID=PPVK6RY4NB7N6K8WS340

If that is true, I wouldn't worry about leaving the water pressure on over extended periods, they're intended for that type of use. Give the bath a few minutes of water every day and enjoy! I like that.