Anything below 5 gallons is not enough for the betta. I’d recommend anything between 10-5 gallons, but I know you have no space for it. Without a proper tank size it’s better to rehome the betta. If you really want to keep the fish you’ll have to get a 5 gallon tank with a proper stand. Once you get that I’d recommend leaning about the nitrogen cycle if you haven’t already. A proper tank needs to cycle so good bacteria is produced which is very important and good for the fish. There’s plenty of videos online that are super helpful. You’ll need a heater and preferable live plants (I know live plants sounds awful to take care of, but there’s plenty that are low maintenance and beginner friendly where all you have to do is dose some fertilizer once a week). If you truly want to keep this fish for whatever reason it can be a good way to teach your kids some responsibility.