Translation:He definitely wants to get married in a church.
If I get the concept right:
- he wants to get married = li volas edziĝi. (lit. he wants to become a husband)
- she wants to get married = li volas edziniĝi. (lit. she wants to become a wife)
- they (♂♀) want to get married = ili volas geedziĝi (lit. they want to become spouses/husband and wife)
- they (♀♀) want to get married = ili volas edziniĝi (lit. they want to become wives)
- they (♂♂) want to get married = ili volas edziĝi (lit. they want to become husbands)
And you can also use it like this:
"la fratinoj amas siajn koramikojn, kaj volas edziniĝi" (the sisters love their boyfriends and want to get married [with them])
i.e. "ili volas edziniĝi" can imply getting married to eachother, but not necessarily.
(Edit: The following usage is apparently controversial according to Arbaro.)
I think you can technically also use geedziĝi for a single person. "Li volas geedziĝi" probably implies "he wants to become husband and wife [with someone else]."
For everything except your last paragraph, you're 100% right. When talking about "geedziĝi" for a single person, well, that's a little more convroversial. A lot of people use it that way, but a lot of other people think it's wrong. The PMEG talks about it (in Esperanto) here:
I guess using the adjective of the religion + preĝejo should work for designating a generic place of worship for one religion.
But for the precises ones (church, cathedral, etc) there are translations https://en.wiktionary.org/wiki/Category:eo:Places_of_worship
Two things, I think: (1) You've put the adverb ("necessarily") in an awkward place for English (unless you're changing the meaning of the sentence); it probably belongs in front of the modal verb ("wants to"), which is the same place it is in the Esperanto sentence (before "volas"). (2) "Necessarily" may be a translation of "nepre" in some contexts, but not in this one; this sentence is not dealing with any actual necessity, but rather just with this guy's feelings: he's insistent on getting married in a church, but it's not impossible to get married somewhere else. So go with "definitely" rather than "necessarily."