if the christian people accept tawhid & they reject trinity................yes they will go to jannah (islamic heaven)
true meaning of islam are submission to one God....
all sabian,christian,judaism,muslim & all human/jinn who accept Tawhid/God Is One & they reject atheist/polytheist/trinity even they never heard about islam will enter paradise
Those who believe (in the Qur'an), and those who follow the Jewish (scriptures), and the Christians and the Sabians,- any who believe in Allah and the Last Day, and work righteousness, shall have their reward with their Lord; on them shall be no fear, nor shall they grieve. (Holy Quran 2.62)
Ubadah bin As-Samit (May Allah be pleased with him) reported: Messenger of Allah (sallallaahu ’alayhi wa sallam) said, "He who bears witness that there is no true god except Allah, alone having no partner with Him, that Muhammad is His slave and His Messenger, that `Isa (Jesus) is His slave and Messenger and he (Jesus) is His Word which He communicated to Maryam (Mary) and His spirit which He sent to her, that Jannah is true and Hell is true; Allah will make him enter Jannah accepting whatever deeds he accomplished". [Al-Bukhari and Muslim].
non-muslim people who never heard about islam but they accept Tawhid/God Is One.........will enter paradise.
Like abraham he found Tawhid is the truth & polytheist is wrong, when he still young & before he became prophet.
Al-Bukhaari (44) and Muslim (193) narrated from Anas that the Prophet (blessings and peace of Allah be upon him) said: “Whoever says Laa ilaaha ill-Allah (No God except One True God & He is Allah SWT) and has in his heart goodness the weight of a grain of barley will be brought out of Hell, then whoever says Laa ilaaha ill-Allah and has in his heart goodness the weight of a grain of wheat will be brought out of Hell, then whoever says Laa ilaaha ill-Allah and has in his heart goodness the weight of an atom (or a small ant) will be brought out of Hell.” (Sahih Hadith)
Non-muslim people who never heard about islam or received wrong version of islam & they are non-tawhid/non-monotheist people...will enter al-araf (border between hell & heaven). No happiness & No Suffering in al-araf.......very silent place
all children from muslim & non-muslim parent who died before reaching puberty........will enter jannah
The Prophet (صلى الله عليه وسلم) said: “Last night, two people came to me and woke me up and said, ‘Let’s go!’ So I set out with them, … We went on, and came to a well-flourished green garden with all kinds of spring colours, where there was a man who was so tall that I could hardly see his head in the sky. Around the man was the largest number of children I had ever seen. I said to my 2 companions: ‘Subhaan Allaah! Who they?’ … They said: ‘As for the tall man who was in the garden, that was Ibraaheem (عليه السلام). As for the children who were around him, those are all the children who died on a state of fitrah (natural disposition).'” One of the Muslims asked: “O Messenger of Allah, what about the children of the disbelievers (Non-Muslim)?” He said: “And the children of the disbelievers (Non-Muslim)” (Bukhari)
insha Allah SWT