A mother cat will leave her kittens when the time has come to do so. They will not stay together forever. This is completely normal & natural for them. So do be prepared that momma will leave. As for the kittens...you say it is very hot during the day so they will most likely stay in hiding where it is cool. Your best chance at seeing them will be in the evening when it gets cooler. You can just go out and sit quietly for awhile, maybe read or something. They will come out to eat & get some 'freedom' & 'activity' in the evening.

Green beans won't hurt the kitties at all. My cats that eat wet food all eat veggies. They eat carrot, peas, green beans, spinach, pumpkin, squash, potato & even some rice. These things are in their high quality, natural cat food. I give them wet food that is only rice, cooking liquids, meat, & veggie. It is all natural. So, if you want to give them meat with any of those things it is ok. Just make sure it has no extra stuff (spices etc) in it. Lots of people make their own cat food for their kitties because it is better than canned food which has all kinds of preservatives & additives & fillers.

This is the food I feed mine. They like the 1st one (natural) the best. They eat dry food (Royal Canin Fit 32 & Sensible 33) with it to give them a completely balanced diet.

I feed the momma cat I am caring for this. And she gets this with it as well as this. (Gimpet cat milk)

You are doing a lot for them by providing them with extra nutrition and giving them a better chance of surviving than just doing nothing. So, know that you are doing a good thing.