My daughter & Son-in-Law are not finding compatible with each other for the last few years and are on the verge of breaking. They are married strictly as per the customary practice of Lingayat community (Fully discussed in the Supreme Court decision referred below) duly performed by a community priest.
My advocate advised that the Supreme Court in a recent decision rendered in the case of Shakunthala Bai and another Vs. L.V. Kulkarni and another reported in AIR 1989 S.C. Page 1359 has upheld the customary divorce prevailing in Panchamasali Sub-sect of Lingayat community, hence they can take divorce, or dissolve their marriage as per their custom without recourse to the Court of Law.
It is well established by a catena of judgments of the supreme court and many High courts that customary divorce is legally valid if the prevalence of such customary divorce, in the community to which parties belong, is fully established [Subramani And Ors vs M. Chandralekha AIR 2005 SC].
The customary divorce takes its validity from section 29(2) of Hindu Marriage Act as “Nothing contained in this Act shall be deemed to affect any right recognized by custom or conferred by any special enactment to obtain the dissolution of a Hindu Marriage, whether solemnized before or after the commencement of this Act.”
Yamanaji H. Jadhav v. Nirmala,  2 SCC 637; Supreme Court held that “Public policy, good morals and the interests of society were considered to require and ensure that, if at all, severance should be allowed only in the manner and for the reason or cause specified in law, with only exception where it is recognized by custom.” If a custom prevails in the community which provides an alternate process of divorce which is not contrary to the law of the land is valid.
Shakuntalabai And Anr. vs L.V. Kulkarni And Anr AIR 1989 SC 1359; in this case, the issue was the validity of customary dissolution of marriage as per the custom of “Udiki form of marriage”. Supreme court upheld the custom of Udiki prevalent in Panchamasale sect of Lingayat community.
You may go with the custom and prepare a divorce deed. Such deed should be signed by the parties to the marriage in presence of two witnesses and thereupon get registration of the deed. Such deed is legally valid and acceptable in every court as evidence of dissolution of marriage.