You are finding that homes built to the family of the 1950's and 60's and in now way able to meet the needs and expectations of today's family.
Your best approach will likely be to find a total solution for the problem. Today's needs include a two bathroom scenario at the very least. With this said, the locations of such facilities should be a major consideration and you'll likely find (hopefully not too late) that having baths in the basement and second level will not get it done. Future buyers will see this as a huge inconvenience and render your home as likely flawed for the RE market.
With this said, in my opinion your absolute best choice is to "bite the bullet" and do what needs to be done to locate the bath where it should have been in the very beginning....on the first floor.
Good luck with your decision.
I am doing the same thing at my house now. I am assuming the lower level is finished. By all means add the 3/4 bath. Most comps in the Highland area show an $8,000 to $10,000 return on the investment (plus happier daughters!).
I am assuming that the bedrooms are all upstairs where the bathroom is. That works just great. IF YOU had 2 beds on the main floor like some other older homes in Highland (like 1 1/2 story) it is perfectly fine to have a full bath on the main.
And same goes for downstairs. If it is fully finished with a bedroom you should put one in there. My guess is that may also be where much of the entertaining goes.
So bottom line just think practical. Buyers will want the same thing you want: bathrooms around the bedrooms, and 2 baths are almost essentially for a family of 4.
If the space you use most is the main floor for entertainment, and there is no bathroom, then down the road I may think of adding a powder room as well.
You also have a good quote, and living in Highland Park you will actually make money on your investment depending on the home and the lot you have.
I have expanded my home in 2006 adding a full bath upper floor and a powder room on main floor-Having 2 daughters and a wife I felt the added bath was essential!
1) Is the basement presently finished?
2) If the basement is not finished, would you expect to utilize a finished basement?
3) If the basement is finished, do you have any bedrooms in the basement? If so how Many?
4) If the basement is finished, do you utilize the finished basement?
I ask these four questions for many reasons, first, to evaluate if a finished bathroom in your basement is worthwhile to you and your family, second, will the bsmt bath add value to your property in the future or three, will a bsmt bath be a positive factor in gaining showing traffic and lastly, will it influence the length of selling time on the market when you do choose to sell the home.
I will provide my thoughts, once I understand your answers to these questions?
Those are my thoughts! Have a great day!