I wouldn't recommend HSBC! We moved to the US last year, a central London branch had supposedly set up a dollar account for us linked to our UK £ accounts and when we arrived, it was non-existent! They'd managed to set up another £ account somehow, no one here could resolve things - cue a hasty trip to another local bank (PNC in our case) to open accounts to transfer a few thousand £ to. So much for the world's local bank - I was so annoyed, I closed my UK accounts with them.
On a positive note, if you have a UK Amex card, Amex here will issue you with a $ card sent out recorded delivery to arrive the next day. Amazing service.
Anyway, I digress. Moving here, I would sell all your UK electricals and plan to rebuy due to the voltage. We have left some stuff at home with friends/family but to be honest, by the time we move back, everything will be out of date (eg TV) so we'll end up buying again there.
If you bring children's DVDs etc, make sure that when you buy a DVD player here, you get a multi region one or you won't be able to watch them.
I would also recommend getting an accountant here (and in the UK depending on property income etc) as we have now been here a year and have just about sussed the system (and are due a huge rebate due to DH being massively overtaxed all the time we've been here). The systems are complex and you need an expert who knows the two inside out IMO. Ours was great and managed to file for us as residents for 2012 - needing to be here for more than six months of the year. As we'd arrived mid July and the tax year ends in December, this could have been tricky. However, he was able to use the dates of recce trips we'd made to push us over the six month mark - certainly something we'd have known nothing about if we'd tried to file ourselves.
Ditto an accountant back home if you move part way through the tax year and have various income streams.
I would also brace myself for a lot of bureaucracy and frustration. There are great things about the US but the bureaucracy we have encountered here is something else! It will be tough for the first few months, there will be times when you just want to go home, but it will be fine in the end!
A couple of useful websites include diapers.com and zulily.com for children's stuff. Don't bring nappies etc, get next day deliveries on everything. We didn't have a car initially, but sign up for Zipcar in advance of arriving here, even if you just use the Zipcar to trawl garages one weekend when you need to buy a car. Everyone drives here, it is pointless trying not to!
Good luck with the move and feel free to PM me!