I think it would be extremely unkind to your dc tbh. It's like purposely inflicting a "broken home" on them. Do you envisage them living with both, one weekends, one weekdays? Or to you want one to have custody, grow to love and consider your child their own, but always have to have someone from outside the home agree on which school, whether or not they have an operation, if the can go abroad on holiday...? What if the main guardian, or other, wants to move to the other side of the country or emigrate?
Either would be extremely unsettling. I personally wouldn't take on a guardianship role where I had to run my decisions past anyone else, it's unreasonable to expect them to.
Joint trustees is fine for big financial decisions.
May I suggest you do videos for your dc or perhaps as I do, write them a letter each birthday about what I've loved about the preceding year and how much I love them.
Of course you can tell a prospective guardian your hopes and dreams for your dc, but you can't tell them how to bring them up. You chose them as someone you respect who has similar values and loves your dc, and is willing. If you suggest things for your dc in the future that they wouldn't have chosen, it's unfair IMHO. They'd probably not do it but always feel guilty, or worse still they'd do it always feeling it was wrong. They'd be fitting into a new family and can't have different rules/expectations to the other dc.
Chose well, one guardian, accept that they will do as they see fit. Enjoy every day and let your dc know they are loved. That's all you can control.