Hello Scott, my name is Pete good to have you on board from Sunny Hong Kong, its always nice to have an expat on the forum, and I am sure I can answer your questions.
There is no problem with registering your childs birth at the Embassy, the child is automatically entitled to British Citizenship, since you and your wife are legally married.
You will also be able to obtain a passport no problem for your child, as for your wife's entry to UK, even though she has had visitors visas before, and as your relationship is probably over 4 years, although you married in 2005, which means your marriage is close to 3 years now, your wife just has to apply at the nearest British Embassy, preferably Hong Kong to speed up the process, for an entry clearance visa as your wife, you will find the process is slightly quicker for her than a standard spouse visa.
Your advice received about applying for a visitor visa is extremely bad advice and if you do this, you cannot adjust status in the UK.
So please don't take that advice, its wrong and will cause you problems.
The last thing you want is once your wife is in UK she then has to leave the country and apply in the Philippines, thats a waste of money.
No the correct advice is for you to apply whilst in Hong Kong, that is the quicker route and I hope you take my advice, your entry clearance visa for your wife should be issued no problem at all, and is valid for 24 months, you may then adjust status in UK to permanent resident after 2 years.
Your child is born to a Filipina, so technically the child is entitled to be registered as a Filipino citizen, so that should not be a problem, your child can have dual nationality, and have 2 passports, so go ahead with that if you wish, what you will find is that if your child travels on a British passport on entering the Philippines, your child will also benefit from the balikbayan privilidge of 1 year entrance without let or hindrance.
Good luck Scott and let us know how it goes.