I don't know how hot it will be for you guys in summer. We live in the middle of no-where and singlets/short suits and nappies will be what our bub wears for the first wee while.
Darcy wore 00000's for a few weeks and 0000for about 10 weeks and she was average. I had to send my mum to get some stuff ofr her while I was in hossy. Then she did this huge growth thing and nothing long or with feet fitted her, so even tohugh you estimate they throw you.
The basics are failry cheap though so have a ocuple on hand and then grab what you need.
Remember Bonds anything you need to upsize one size.