I assume you understand that entering a Church (especially for religious services) is forbidden by many sources and contemporary rabbanim (see e.g., R Doniel Neustadt summary or Halachipedia here) and are asking whether doing it to please one's non-Jewish father becomes permitted?
Rashi learns from the verse (Vayikra 19:3)
You shall each revere his mother and his father, and keep My sabbaths:
I the LORD am your God.
Scripture places the commandment of observing the Sabbath immediately
after that of fearing one’s father in order to suggest the following:
“Although I admonish you regarding the fear due to your father, yet if
he bids you: "Desecrate the Sabbath", do not listen to him” — and the
same is the case with any of the other commandments. This, it is
evident, is the meaning since Scripture adds "I am the Lord your God"
(the plural) — both you and your father are equally bound to honour
Me! Do not therefore obey him if it results in making My words of no
From this I understand that one shouldn't overcome the prohibition of entering a church because of wanting to please one's father.
A second reason might be that a convert loses his family connection, as such he doesn't have a formal commandment of obeying his father (although he is still bound to honor and respect them, see e.g., here).
As always here, should this be a real question, you should CYLOR.
PS. It is better to have one question per post - I would therefore suggest you split your second question and post it separately. It likely will have a different answer from the one above. In the meantime see some sources here and here.