I was raised Roman Catholic, and despite going through the motions as a child, I always had a ton of questions and never fully believed in god. I was the little kid sitting in Sunday school asking questions that would eventually have them kindly request to my parents to not send me back anymore.
I always thought of myself as an agnostic even before I knew of the term. Atheist is definitely too strong of a term imho, and something people should really consider more closely before making a declaration about. As I've come to understand it, the difference between an atheist and an agnostic is that even if the actual god appeared in front of an atheist, spoke to them, and performed a miracle for them to witness, they still wouldn't believe in god's existence because they already absolutely KNOW god is not real. I really can't see myself just absolutely knowing that fact beyond all doubt (without using some faith ironically).
Majoring in philosophy in university introduced me to a ton of various theories about religion, and I the one that seemed to stick with me the most was from The Ethics by Baruch Spinoza. He so clearly argued that everything (god, universe, substance, nature) is just one whole singular substance that we are all just a part of, and that death is just a transition into a different part of the whole. I always kind of liked that idea of interconnectedness with everything around us.
As far as afterlife is concerned, I think a lot of people don't really consider what a "heaven" or afterlife would really be like. First of all, most people who believe in an afterlife are under the impression that we shed our physical bodies and exist only within our souls (maybe "within" is the wrong word, but you catch my drift). If that is the case, then we as humans truly cannot know what we'd think and feel at that point. Practically, all our wants, needs, desires, beliefs, etc. are based on or around the physical. To suddenly be completed void of all the physical, I'd be a completely different person (or mind, or entity, or immaterial being, or whatever). There is no way I could 100% know that I'd have any of the same feelings or emotions (after all, emotions are just chemical/hormonal reactions in my physical body which I don't possess anymore after death). Would I still "love" my love ones? I honestly don't know. How can one love without the physical? Is it possible? I'm not god after all, who is (allegedly) omnibenevolent (i.e. all-loving).
I'd like to think there's more to the universe than just this existence, but minus any proof I don't think I will be completely altering the way I live banking on an afterlife. I'm just not that type of person, no offense to god, but if god is real, it would know that about me anyway.
Personally, just cremate my remains and get rid of them however you see fit. Or maybe do the "green" burial where they bury my remains but add whatever chemicals to it so it biodegrades and turns into compost quickly, but I'm only cool with that as long as where ever I'm buried that land is actually being used and not just a waste of space cemetery full of headstones that no one has visited for decades - just make it a nice green space/park please.