I am sorry but on this occasion you are wrong. If it is a simple uncomplicated will as the op implies then there are no hidden catches or pressure for you to let them act as trustees or executors. In our case it is an easy to understand statement, me to her, her to me, then on to named siblings if we both go together. If things are difficult for them later should I really worry or do I really care. No.Are you a union member, Unite have a free will writing service done through a company of proper solicitors.
With the utmost of respect-- Nothing is for free.
There are always conditions.
Main condition is that the 'free solicitors' act as trustees and executors. That is when they HAMMER away at what you leave behind.
Will cost your beneficiaries loads.