You can right your will how you wish (cut the kids out altogether and leave everything to the local cats charity !) and the law in England and Wales will only intervene on the application of anyone who is provenly dependant on you. The cats charity would lose some of the whole estate, in my example, to the extent that dependents would need funds .As between children you can give one more than others if you wish.( I did with mine,because one will have greater financial need if I die tomorrow, being only just qualified and somewhat dependent on me, whereas the other is much older and the director of a public company and therefore not at all dependent ).
The only safe and wise thing is to go to a solicitor (not a will writing firm; a former bus-driver with no legal qualifications may be a 'will writer' ) because you need professional advice and the will drafted so no such claim arises.They'll hear what you want and what you have and all the details.By the way,you don't need the solicitor to be a named executor. In case you think it is, it costs vast amounts if you do that since a solicitor executor charges the estate a lot for acting, as do banks (and will writers) named as executors.It's quite unnecessary.Your executors can take such legal advice and help as necessary, without that.