I am Christian, but if there is no God, will I ever see my loved ones again?
The short answer would be “probably not,” which means all should cherish their loved ones while still alive, lest this be your only chance to do so.
Packed within the question are some assumptions that are unverifiable, starting with the presumption that god is the only one possible. Were it the case that, for example, that something like the Buddhist view is correct, there may be some form of cognitive survival, reincarnation etc. Such might even theoretically be the case without any technical gods involved, as part of the natural way of things as neutrinos or black hole singularities (as strange and wonderful in their own way as anything posited in religions).
I doubt those are plausible scenarios, so once again would proceed on the working hypothesis that this life is the one you have to do good or ill in, and should therefore make the most of it with no guarantee of do-overs.
I have said before that I would be delighted for there to be an afterlife, certainly for poor old Franz Schubert, the brilliant composer who died sadly young, a seeming failure. How right for him to be able to know how not a failure he was, that all of his music is known and cherished and performed on a scale he could not have imagined when he died in 1828.
But alas, I suspect poor Schubert really did cease to exist in 1828, and so can never know of his posthumous honor and fame. But we know it, and it is through our memory of his work, our listening to it being performed today, that he lives on. And only by that means can he live on. So its up to us, we are the torch bearers to the future, to a time when all of us will be as not existing as Schubert. We can strive for each of the memories we generate in others to be as bright and warm as the ones we hold for Schubert now.
In the meantime, try and enjoy ourselves … but don’t make a nuisance.
I can't claim to know whether every Memorial Day or Veterans Day observance excludes non-believers from the official observance when religious invocations are done, but it is fair to say we aren't taken note of generally.