Previously there was much more dependence on Faraid law to provide the guidelines for divisions of wealth upon the passing of someone, however recently there has been continued awareness of the benefits and necessities of willing (gerund for writing a will?).
A good website with quite clear reference is at https://janganterlepaspandang.wordpress.com/2009/06/07/wasiat-faraid-dan-harta-sepencarian/ (mostly in Malay). One of the comments does mention that to a certain level, division of the 'peninggalan' can we done via Seksyen Pusaka Kecil which I think is a division under Pejabat Tanah dan Galian for each district. The commenter suggests to go this this section of office and document down a hibah wasiat (hibah = gifting). Some good details provided here http://www.kptg.gov.my/?q=content/pembahagian-harta-pusaka-kecil-0
I will try to call them tomorrow and ask how do you 'pre' assign the divisions (if possible). For Penang it is here http://www.kptg.gov.my/?q=direktori-staff&title=&field_email_value=&tid=142
One of my friends recommend to use the services of WasiyyahShoppe. Will try to give them a call as well.One of my concerns was, the challenge here besides finding a good, reliable, honest 'service provide' lays the question - will the firm executing (if you decide to use a trustee) still be around when the need arises (sooner or later eh).
Some details and elaboration on Hibah - https://zulkiflihasan.files.wordpress.com/2008/06/gift.pdf (note - please verify validity). Also http://e-muamalat.gov.my/sites/default/files/kertas_ilmiah/2010/08/KK_Hibah__Wasiat_21042010.pdf