Answer
(Fatwa: 1814/1440/L=1430)
Yes, a husband can help burying his wife being present inside the grave along with the mahram of wife.
وقال الامام فخرالدين: يكره للناس ان يمنعوا حمل جنازة المرأة لزوجها مع أبيها و اختها ويدخل الزوج فى القبر مع محرمها استحساناً وهو الصحيح و عليه الفتوي (خلاصة الفتاوي: 1/225)
After the death of wife, husband is not allowed to touch her, so kissing wife’s forehead from above the shroud accordingly is not appropriate.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband