Yes, 180k is enough for a family of 5 if you have medical and tuition fees covered. Consider what you will do if you stay long term and your youngest also needs to go to school - would your package change to include another school place? School fees are comparable with fairly expensive day fees in the UK so would quickly impact your budget.
There are expat families in Bangkok on MUCH less than this but also many on far more, and lifestyle will of course massively dictate what you need to live on comfortably. Eating cheaply is easy but as soon as you want imported goods or foreign takeaways, you find yourself spending a lot! Cheese is expensive 
Accommodation costs vary wildly but you would probably be looking at around 50k a month for a big enough condo or a house in a compound. In some areas or if you live in a flashier or newer building, you could double that.
Electricity is expensive, expect to spend at least 4k a month on that, that's what I pay for limited use during the day but 3 ac units all night. Again, I have some friends who pay double that! But water is cheap as chips.
Taxis are cheap and plentiful but school buses are expensive. I would definitely advise choosing accommodation near to workplace and school if possible; if not, I would prioritise school and have your husband take on the commute instead of your children.
Cars are expensive to buy or rent (although rental deals are much better since covid, they are starting to rise again). 15k for a small car on a long term lease would be a fairly good deal. A Toyota Fortuner or similar would normally be 35 but you can get better deals at the moment. Will your husband get a driver/vehicle through work? And if so are you able to use them during the day when your husband is at work?
The only other thing to consider is as a PP suggested - could you negotiate flights home annually or every second year? With a family, that's a big expense. Aim to negotiate for a cash sum rather than the actual flights, so you can use the money to bring people to you or take your own holidays locally if you prefer.
Home help (nanny/cleaner) is cheap and once you have it, you'll never look back!