This is easily enough done with proper legal advice as long as you are very clear on what you want to achieve.
I also recommend (although depending on solicitor it may add to the bill) that you see them to discuss, go away to think through the issues they raise, then go back with your plan clear.
To consider:
How exactly are you owning the house together in a legal sense? This may affect what is considered to be your assets if / when care costs are calculated, and a few other situations - such as your daughter deciding to go to live elsewhere.
Who has the right to remain in this family home and in what circumstances? You could, after both of your deaths, say daughter can remain until her own death / decision to move; but that may affect what money your son inherits.
The issues mentioned about valuing the house are not difficult for a lawyer to write in, but some things can be more awkward - it is easy to get a valuation on a house, but who makes decisions about it if it does not sell at that price?
You also need to consider emotional issues - what level of care or support are you expecting from your daughter (or she from you?). I have known set-ups like this where people have expected a high level of care from their house sharers, and this cannot always be delivered.
There are many families where this works beautifully for all, but do get everything lined up