We will be spending 4 nights in Scotland next year and want to do a day in Edinburgh then proceed to Callandar. The question I have is would you stay the night in Edinburgh then proceed to Callandar or go to Callandar and commute into Edinburgh?

the latter

Are you staying overnight in Callandar? We stayed in a wonderful B&B @ www.westerton.co.uk if you don't have reservations already.

It partly depends on Where you are coming from and how you are arriving.

Flying in? - if so GLA or EDI? Long haul or just up from England?

Driving up - from where?

We are flying into Edinburgh on BA

Then in that case -- visiting Edinburgh first makes most sense IMO. Land at EDI, take the airport bus into the city, explore and spend the night car-less. Next day collect your rental car (either in the central city or take the bus back out to EDI and pick up the car there) and drive out to Callander.

Thanks janisj. Great advice!