According to strict halachah, there is nothing wrong with making sheva berachos not under the chuppah, however, the minhag Yisroel is not to, and we don’t to tamper with minhogim without good reason. If a grandfather is literally wheelchair bound, and it’s impossible for him to get up to the chuppah, and the chuppah can’t be brought to him, and it’s a time and place where no reform movement is up and rising it would seem that in such a case the poskim would allow the berachah to be recited not under the chuppah.
In regards to the shailah of one who has a minhag not to eat out on Pesach, and he gets invited by a close friend and he doesn’t want upset him. He should try and explain that his family minhag is not to eat out, and he should perhaps invite him over instead. If no easy alternative can be made, and one’s friend will be upset and there will be a big issue of bein adam lechaveiro, then I would say that after seeing the two stories about the Chofetz Chaim and R’ Yisroel Salanter about how bein adam lechaveiro overrides minhag Yisroel, it would be ok for one to forego his family minhag and eat out. Provided he is certain that he won’t come to eat chometz on Pesach.
Although outdoors chuppah’s and making a berachah under the chuppah are two different shailos, they are very similar and I guess we don’t want to differentiate between the two.
