Actually, @Leaannb I think that you are getting a rough time on here because this issue is so abstruse and legally technical posters don't know what they are talking about and are unaware of the changes to the way non doms are taxed in the UK, which changed some time ago.
.My solicitor just told me that he will be fine for his first year bit his domicile will revert to UK on the 2nd year is that false?
Yes it is false but I think that the problem is likely to be one of terminology. In the UK "domicile" has almost nothing to do with citizenship or residence. It is an immensely complicated area of law (my specialism) but basically, if your husband saw a US state as his homeland (ie the place where he ultimately he wanted to live once all other things such as work etc were over and done with) at the time your son was born, he would almost certainly be domiciled in that state - its called a domicile of origin.
SO I'm going to assume that your son has UK citizenship from you (ie that you had UK citizenship when he was born), US citizenship from both you and his father and a domicile of origin in a US state. WHen he comes here (if I've understood you correctly) he will have 3 sources of income
US military earnings and benefits
UK income from a Barclays Bank account
Investment (passive) income from the US.
Assuming that he doesn't get the benefit of the SOFA (he needs to check this) then the UK/US tax treaty gives the UK the right to tax it as a UK citizen - the treaty gives them the right to do this for the 10 years after the renunciation of UK citizenship as this would be for tax avoidance reasons. UK tax might well be more than US tax as we are not generous with our allowances.
The Barclays income will be taxable in the UK and the US will need to give credit for the UK tax paid under the tax treaty.
The issue is therefore the passive income in the US which is presumably about $35,000? Here your son has a choice. He can leave this in the US and pay tax on it on the remittance basis (ie no UK tax if he leaves it in the US) but he will then lose his UK tax allowances against all of his UK income or pay tax on it in the UK and claim double taxation relief under the treaty.
So in theory renunciation would help as it would put your son firmly into the SOFA category but would not work for the purposes of claims under the double taxation agreement.
I would strongly urge that he gets advice asap from the military about his dual national status and then seeks specialist advice.