Hi Barry,
1. Generally, the law requires two parties to be separated for 12 months before they can apply for divorce.
2. You can still purchase a house with your wife (ex-wife) as joint-owners after you separate/divorce. Holding a house as joint tenants means that if one of you pass, your share in the property will automatically pass to the other surviving owner an not to your children or to anyone else you leave in the will. If you want distinct and separate shares in the house, so that you can leave your share to anyone you wish, mention in the agreement that you and your wife (ex-wife) hold the property as tenants in common.
3. Draft a financial division agreement with your wife as soon as possible. All your assets (jointly held, individually held) will go into a "shared pool". You will then need to agree with your wife who has what from this pool. Have this agreement in writing and signed. Afterwards, obtain a consent order from court to ensure that it is enforceable.
4. If you cannot agree, you can apply to court and they will divide your assets for you. There are many threads on this site that talk about how courts divide assets upon separation/divorce. You can find them by doing a quick search. You can also have a look at the Family Court website.
5. Similarly, agree on a custody arrangement regarding your children, bearing in mind that your children's rights and interests are paramount and the only thing that should matter when it comes to custody arrangements. Think about visitation rights, who takes care of the children when the other is sick and unable, communication between the parents, medical and psychological visits in the future and whether this will require the notice of or consent by both parents. Again, after you have agreed, get a consent order from court.