from what i heard, in islam, even though u already convert, parents will always be parents, and u still have responsiblity toward your parents and it wont change.... if u ignore them, u still consider anak derhaka...

and in funeral, i heard u can go to other religion funeral to pay your respect... it is not wrong and it is encouraged to do so... just that like bornd said you may do whatever it is as long it is not against the Islamic Teaching...