The kids/baby/twins... can at least nap at the same time in the afternoons....
baby will still be napping in mornings...
but the 3 year old and 20 month old... should still be napping.... after lunch... and the baby can too.
Try to do it that way.
I only have 2 kids... but when I had my 2nd child... my eldest child and then baby.. would nap at the same time, in the afternoon. AND then I got some quiet... at least. or even a nap.
But yes, with naps, the day revolves around that and because you have 3 kids.
Could you possibly have family/friend come over... and just help? Even if just for company for you... having another "adult" around... often helps... and helps Mom to stay sane.
ALSO... start incorporating the 3 year old and twins... INTO simple duties/chores around the house. Just simple stuff. The goal is not that they do it perfect... but "indoctrinating" them into... the 'role' of them doing chores too... and HELPING.... Mom/the family.
My kids... somehow feel "important" when I designate things for them to do around the house. Even if it is, chores. And they do it... because I make it like a "project" for them... 'framing' it/the project... as something "fun" .... not drudgery. If you start now.... then it will help in the long run... so that THEY TOO... help around the house... and it will be... a more everyday.... thing to do. Not pulling teeth about it.
Also... even if just playing with play-doh... make a 'routine' for them... say "In 10 minutes, its Play-Doh Time!!" and on a table, put it out... and then they can do that. And let them do that... until they lose interest. For example.
Or say "after breakfast is coloring time!" Make excitement in your voice... and then put out their coloring books and crayons... and let them go at it.
Or say... "after you put away.... (wink)... its baking time!" and just make dough for them... to play around with on the kitchen table.... not necessarily "cooking" but just pretend cooking....
Or "In 10 minutes its puzzle time!" And take out their chunky toddler puzzles.
The 20 month olds...can't DO crafts.... per say... but you CAN just let them glue stuff, or scribble on paper plates etc. It does not have to be literally.... doing crafts like in the instructions... just to keep them busy. And then they will also be inadvertently... working on fine-motor skills... for example.
I know... easier said than done.
But for your 3 year old... I think its also important for him... to HAVE time to himself... not having to share. I tell my eldest she does not have to share.. nor everything. It is HERS and if something is special she does not have to. Her "things" are not across the board... for "everyone." AND I let her 'choose' what to share... or not. A child... NEEDS to know that too... that THEY can or do not have to... share. Everything. It is their things.... I also tell my 4 year old that. They 'need' a sense of boundaries too... and having a say in, what they choose to share or not.
If your 3 year old is going nuts... with the younger ones.. let him, be by himself or in his room.... and have respite or do what he wants. My eldest, my daughter, does that with my 4 year old. She will tell him "I want to be by myself now..." and then she does, we respect that... and my 4 year old has also learned to SAY things too.... like that. Its okay. Sometimes kids just do not want to be all mingling... or in each others proximity...
Well, I don't know, I know its not easy... you have 4 differing aged children... I HOPE... your Husband.... babysits too??? And so that YOU can get time-off... and have your OWN time... by yourself... home or not... to do what you want.
That is really... needed.
all the best,
Susan