Linking surveys

Hi everyone,
I have 3 types of surveys which I would like respondents to complete - teacher survey, parent survey, child survey.
I would like these surveys to be linked together so I know who is in the same class and in the same family. How do I go about doing this (especially with multiple children and both parents who want to take part).
Can the respondents then take the surveys at any time e.g. child 1 takes it after school on Thursday, child 2 takes it after school on Friday etc. or does it have to be in the same sitting? What happens if they have limited devices on which to take the surveys?
Since the children are younger than 15, they would need parental consent before they do the survey. Is it possible for the parents to click yes, they consent for their child to do the survey, then somehow they get a link or something for the child to complete? This is quite hard, as they need to note the link down?
Thank you so much in advance for your help!