For children, - Regretting on the Day of Judgment in Hereafter (Akhirah) for not following Deen-e-Islam

Once, a group of people were traveling on rocks at night. A voice came
from the sky that whosoever picks up the rocks will regret and
whosoever doesn't pick up the rocks will regret. Now, the people were
confused. How can this be? Whether you pick up the rocks or not, you
will regret!
Anyway, some people picked up the rocks and some didn't. In the
morning when they reached their homes, they saw that the rocks turned
into diamonds. Now, those people who didn't pick up the rocks started
regretting saying, "If only we had picked up some rocks." Those people
who did pick some rocks also started regretting saying, "Why didn't we
pick up more rocks?" Both sides ended up regretting.
Dear Muslims, this same incident will take place with us on the Day of
Judgment. Those people who spent their time in useless things will
start regretting by looking at those who achieved a great position in
Paradise by spending their time in the way of Allah (SWT). Now, those
who did achieve a position in Paradise will start regretting by
looking at those who did more than them and are higher in status.
"Alas! If we had only done more to please Allah (SWT)."
Allah (SWT), the Majestic said: "And could you but see when the guilty
shall hang down their heads before their Lord: Our Lord! We have seen
and we have heard, therefore send us back, we will do good; surely
(now) we are certain." Noble Qur'an (32:12)
Imam Sadiq (as)said: All evil is placed in a house and its key is love
for this world. All good is placed in a house and its key is
abstinence in this world.

For children, - Islam: Death is a Beautiful Gift for a Believer and this worldly life is a preparation for Hereafter

According to an old fable, a man made an unusual agreement with Hazrat
Izraeel (pbuh) - the angel of death. He told Hazrat Izraeel (pbuh)
that he would be willing to accompany him (as though he had a choice)
only if Hazrat Izraeel (pbuh) would send him a notice well in advance.
The agreement was made. Weeks became months and the months into years.
One bitterly cold night, as the man sat alone thinking of his success
in life, Hazrat Izraeel (pbuh) tapped on his shoulder. "You are here
too soon" the man cried out. "You sent no messenger. I thought we had
an agreement!" Hazrat Izraeel (pbuh) whispered "Notice your hair, once
it was full and black, now it has streaks of silver in it! Observe
your face in the mirror and see the wrinkles. Yes! I have sent many
messages through the years! I have kept my part. I am sorry that you
are not ready for me but the order of Almighty Allah (SWT) cannot be
averted!"
Prophet of Islam, Muhammad (pbuh) said: You are not created for
annihilation and mortality, but you have been created for survival and
eternal living, and it is only by death that you are transferred from
this lodging to other housing.
The King and the Poor Man are equal after Death in this World:
There was a king who decided to take a tour of his country. As he
passed by different places, everyone rushed to see him. However, while
passing by a certain place, he noticed a poor old man who did not pay
any attention to the king's arrival and remained engaged in his own
activities.
The king went up to this poor man and asked why he did not join the
people to see him. The poor man replied, "Before you, there was
another king who once passed by this place. Everyone gathered to see
him as well. But, few days later he died and was buried in a place
nearby. A poor man also died during that time and was buried near the
king's grave. After some time, a strong flood passed through that area
causing those graves to overturn. As a result, the bones of the poor
man became mixed up with those of the king's. We could not
differentiate between them any longer. After seeing this, it does not
matter to me anymore as to who is a king and who is a beggar. In the
end, our home is the same."
Imam Zein elabdin (as)said: The world and its affairs will seem
insignificant for the one with great and cleric personality.
Imam Muhammad Bagher (as)said: To recognize the world insignificant is
the highest stage of certainty in faith.
The Hereafter - Ma'ad by Ayatullah Dastghaib Shiraazi (q.s.)

Dua when waking up at night

شَرِيكَ لَهُ ، لَهُ الْمُلْكُ وَلَهُ الْحَمْدُ ، وَهُوَ عَلَى كُلِّ
شَيْءٍ قَدِيرٌ ،
سُبْحَانَ اللهِ وَالْحَمْدُ لِلهِ ، وَلَا إِلَهَ إِلَّا اللهُ وَاللهُ
أَكْـبَرُ ، وَلَا حَوْلَ وَلَا قُوَّةَ إِلَّا بِاللهِ الْعَلِيِّ
الْعَظِيمِ
رَبِّ اغْفِرْ لِي
Translation
The Prophet (peace and blessings of Allah be upon him) said:
"Whoever wakes up at night and says:
'None has the right to be worshipped except Allah, alone and with no
partner, to Him belongs [all] sovereignty and praise, and He is able
to do all things;
How far from imperfections Allah is, and all praise is for Allah, and
none has the right to be worshipped except Allah, Allah is the
greatest, and there is no power nor might except with Allah, The Most
High, The Supreme.'
and then supplicates:
'O my Lord forgive me.'
will be forgiven."
In another narration:
"and then asks [for something], he will be answered. If he then
performs ablution and prays, his prayer will be accepted."
Transliteration
laa ilaaha ill-allaahu waḥdahu laa shareeka lah, lahul-mulku wa
lahul-ḥamd, wa huwa ‛alaa kulli shay'in qadeer,
subḥaan-allaahi wal-ḥamdu lillaah, wa laa ilaaha ill-allaahu wallaahu
akbar, wa laa ḥawla wa laa quwwata illaa billaahil-‛aliyyil-‛aẓeem
rabbigh-fir lee
Sources: Abu Dawud No# 5060

Dua when waking up

بَعْدَ مَا أَمَاتَنَا وَإِلَيْهِ النُّشُورُ
Translation
All praise is for Allah who gave us life after causing us to die, and
unto Him is the resurrection.
Transliteration
alḥamdu lillaahil-ladhee aḥyaanaa ba‛da maa amaatanaa wa ilayhin-nushoor
Sources: Bukhari No# 6312