Welcome to the forum. I would feed them every day and I would leave a bunch of fruitflies running around in the tank with them so they can eat at their leisure. You can block out the lid of the tank for a few hours to prevent the escape of the flies and it won't do any harm (just remember to unblock it).
You could just let them go in the area, since they are from there.
If you wish to keep them as pets then you will need a modestly sized vivarium - the taller the better. A small vivarium would be adequate while they are young but the bigger they get the bigger the vivarium will need to be. There is plenty of info in our Gray Tree Frog article.
Also, don't forget to dust the flies with vitamin/calcium dust regularly - again, there is info in the article. Fruit flies, in my experience, are not the greatest growth food so consider adding gutloaded crickets to the froglets' diet.