I meant to mention in my last post that the law in most countries allows wills to be written out by hand and your signature witnessed by two people. Most drug stores sell simple forms that all you do is fill in the blanks. There is a large space at the end to write in anything personal, plus you can add a codicil any time you want. That is because circumstances change all the time and it saves the bother of starting from scratch.
When it comes to leaving someone in charge of your childrens future, ALWAYS get a lawyer. The expense is small compared to the peace of mind you will have.
The key point here is the care of children in the case of your death.
UK law allows a parent to state in a Will that they
"I appoint XXX as sole (or joint with YYY) guardian of my child / children (names) until he she or they attain the age of 18 years" This provision is applicable to adopted children in addition to childen of a marriage/relationship.
Courts are bound to respect this provided the will is properly witnessed etc The appointed guardian(s) must be over the age of majority and capable/competent for the role In non-UK regions local guardianship law applies - however a will clause that XXX be appointed guardian in case of your death is generally held as strong reason to appoint that person in most of the US.
Without any such clause imn a Will in the UK the social services department locally can arrange for care / guardianship - often at variance to what you would have wanted - make a Will - include a Guardianship clause - have it signed and witnessed and properly stored