What size bolt?

[Throbbinhood]

Sounds like you've been busy mate.
No, I don't have a clue about the baby seats(I've never been a baby )
I'm sure few blokes with toddlers or who used to have babies before they outgrew them know the exact answer.
Cheers

P.S. I'm sure baby's thriving at super fast growth phase and walking around the house by now.

Yeah mate, always something going on in this crazy life! Yeah, the young fella is growing too quick! Almost walking.. Time flies!