OP. The people on reddit are not invited to your wedding. Our opinion doesn't matter. If you, your fiance, minister, and the 19 other guests(not including the sister since she gave her opinion already) are okay with paying $10 to park and walk a mile with a camping chair then do it. Talk to each of them personally and feel it out. Wedding ceremonies in nature are worth it imo. A lot better than a chapel. and guess what, if they don't want to come then you and anyone who does can enjoy the canyon wedding and do a reception afterwards. It's you and your fiances wedding not theirs. Don't let them decide how it happens. They're going there to support the two of you, and if they can't make the hike that doesn't mean they don't support it. Just that it may be too much for them. Don't let that stop you