Possibly not the best option for you, then, if you’re not looking at paying over the tax threshold. You’d get more interest from a normal kids savings account. Best rate for a Junior ISA at the moment appears to be under 3%, while kids savings accounts can be found at 4% and 3.5% for regular savers (monthly limits on deposits) and 3% for easy-access (no deposit limit).
As ever, MSE guides are very helpful, I find - junior ISAs and savings accounts.
I would perhaps avoid the “sticking it in own ISA” route because you don’t know what might happen in the future, and events might transpire that your kids don’t get the money. That’s a large advantage of separate savings accounts or ISAs, I feel - anything happens to you, money belonging to your kids is ringfenced and they cant’t lose it.