The key to surviving Death House with new players is being very explicit about what players need to know.
The key to surviving without a dedicated healer is realizing that there are few time constraints and plenty of opportunities to rest.
This answer assumes the reader is a game master with a problem similar to the of the OP. Many spoilers are ahead.
Death House is like an old school dungeon in that the monsters remain in their rooms until 'activated' by the characters - this makes a bit more sense then normal, as most of them are either dead and haunting the place of their death, or are constructs and were ordered to defend a specific spot. Many or most of them will pursue the PC's once 'activated', but none of them will go looking for the party until it makes first contact.
However, unlike an old school dungeon, Death House has no wandering monsters and at least two floors of the house are quite comfortable places to rest. There are oil lamps and fireplaces; there is even a well-stocked kitchen the party can draw on.
Thus, the key for a small party or a party with no healer is simply not biting off more than they can chew. Exploring slowly and carefully, and when they fight monsters, fighting them one encounter at a time. When the combat is over, taking short and long rests as needed to replenish hp and spell slots. There are even actual beds for them to sleep in, if they dare.
The opposite approach, pushing on when low on hp and spells, or fleeing from one encounter into a previously unknown part of the house and thus activating a second encounter before the first is resolved, are great ways to die quickly.
The first two floors of the house, while creepy, are completely benign. What's more, they contain everything the players need to rest indefinitely except water (and there is water in the basement that may be accessed without a single encounter). The third floor contains three combat encounters, but of single monsters. The attic contains one potential encounter of a single monster if it was not found on the third floor. There is also an encounter with a pair of monsters in the attic that may possess party members but which will not damage them. Even if all of these encounters are avoided, the party will level to second when they find the entrance to the basement.
The basement is where things get more difficult, but if inexperienced players have learned the lesson of "rest to restore hp" they should be alright. In the basement the monsters get tougher and three of the six encounters are of multiple monsters at a time. The monsters in each case of multiple foes are undead, so the ability to turn a few and concentrate on the others will be very helpful, but even if the party does not have someone who can turn, most of the monsters are not intelligent. The party should be able to use the furnishings and narrow passages to reduce the effects of the monster's numbers, and then should be able to retreat to the house above to rest after each encounter - there is even a shortcut to the house available.
The ghasts in the basement are a difficult encounter - fortunately the party may have access to a scroll of protection from poison from the house above. The treasure from the ghasts will go a long way to helping the party if they decide to fight the single monster in the sub-basement.
That 'boss' encounter, a CR5 shambling mound when the party is likely at second level, could easily be deadly if the party insists on melee. However, by this point they should have learned the lesson of using their environment against superior but unintelligent foes. The 'mound is blind beyond 60 feet, has a poor movement rate, no missile attack, and no resistance to most of the party's missile attacks. The encounter is begun in a room that is encircled by what is effectively an archery platform and which has both a closeable door and a portcullis through which the characters can unload missile fire without the 'mound being able to immediately follow. The shambling mound lacks only a 'Kite me' sign on its back.
All of the strategies described in the paragraphs above can and should be used by a party of clever, experienced players. But the OP posits the challenge of very inexperienced players. In this case it is up to the GM to encourage the players to learn, without spoon-feeding them. It is quite possible that their first combat in the house will be their literal first combat as players. When that combat begins, a DM for complete novices should absolutely say "This is your first combat - let's run through the rules for combat and see if you have any questions. What do you think will be the most effective way for you to deal with this monster?"
When the combat is over, if characters are wounded, the DM should say, "Some of you are wounded (or unconscious). What are some ways you can recover hit points?" If no one suggests resting, the DM should then explain the resting rules, as well as their advantages and disadvantages, without outright suggesting that the players rest.
It is quite possible that a new player's first combat with multiple opponents will be with four ghouls or five shadows. That is hard. At the outset of the combat, the DM should pause things and say, "This is the first time you have fought multiple opponents. How do you think that will make the fight more difficult? What can you do that might help you counter these advantages?"
After each use of a new feature or ability, the GM should say "what did you learn here that might help in the future?" After enough of these prep and debrief sessions, clever novice players without healers will be equipped to do quite well in the Death House.
