I cannot work out where you live, but that does not really matter.
In your place, I would wait until my have either moved, or chosen where they want to move to. If they can give you any idea of the places they are considering, you can start looking at house prices there now.
As you are fed up living in your present house, this is the right time to consider a move, once you know where you want to be. But find out now what money you can re asonably expect to have when you go house-hunting.
When they have moved, go to pay them a visit or stay for a week in a bed and breakfast in the town and see what you think of the place.
Right now you could consider contacting two or three estate agents in your neighbourhood and get and idea of what sort of price you can expect realistically to sell your house for in its present condition.
I would not follow advice to do costly repairs or alternations before selling. You will not recoup the expense in the sales price, if you do.
Start deciding what stuff you will get rid of before moving, and dispose of it before the house is to be shown to prospective buyers - the less clutter the better, at that point.
Make sure that attics, cellers, crawl spaces are accessible and not chock -a-block with odds and ends.
How old is the son who lives with you at the present moment, and how does he feel about the move. Will he be moving with your, or finding his own accomodation where you are now?