Can I designate a space in the Sukkah for storing kids’ stuff like bikes and toys and drinks and stuff
Items that are disrespectful to the sanctity of the succah should not be in the succah. As far as I know designating a place for them doesn’t help. What you can do is to put up a proper mechitzah, then that part of the room won’t be in the succah.
As a side point, it is permitted to store drinks in the succah, bikes are not appropriate. Regarding toys, I don’t know what kind of toys you are taking about, and I don’t know what stuff means.
Have a kesiva v’chasima tova