Family lawyers are prevented by their professional conduct rules from acting for/advising both parties when a marriage or relationship comes to an end. If you and your ex are fortunate enough to be able to sit down together to discuss the end of your relationship, the arrangements for your children and finances and reach agreement about all of that, it is sensible for at least one of you to obtain legal advice about your proposed arrangements to find out if they are in your best interests and will work.
Getting advice from a family lawyer about what you and your ex have agreed does not mean that he or she will drive a coach and horses through that agreement. They will give you advice as to how reasonable, practical and fair those arrangements are given your particular circumstances.
Despite what people may think, the vast majority of family lawyers, myself in particular, are not in the business of unpicking and creating difficulties when a couple have gone to the trouble of trying to reach agreement between themselves. We would not however be doing our job properly if we did not tell you about any potential problems and pitfalls in the agreement that you have reached. It is also my job to tell you how those problems/pitfalls can be resolved or at least give you some alternative solutions.
If you choose to get legal advice, your ex-partner does not necessarily have to do so, it is becoming more common for family lawyers to deal with ex partners who are acting in person.
It can sometimes be the case that I will advise a client that I do not consider the agreement that they have reached to be in their best interests. In relation to financial matters, I always want to make sure that they are not selling themselves short and that any agreement will provide at least the basis of a secure financial future. At the end of the day, it is up to you to decide whether you are going to take my advice. It is worth bearing in mind that sometimes it is not always about the money or what you feel you are entitled to, it is about a dignified ending to a marriage on terms that you can both live with and move forward from.