There’s no requirement for everyone on a PNR to check in together but the person checking in can only drop bags up to their allowance not everyone’s unless they have your passport in which case you can use the automated bag drop but then you’re without your passport for when you eventually check in which isn’t a problem for HBO as you don’t need it to pass security but I don’t know if there are extra rules for people with young kids from a safeguarding perspective.

To be honest it’s just easier for you to take your smaller bag with you later and check it at the F wing.