I'd say bus is the better option. The train station in Musselburgh is actually quite a distance from the route. 26 bus goes from Princes St to Musselburgh for £1.60 (need exact change) and takes about 30 mins though I guess there might be some disruption on Sunday due to us runners getting in the way!. Lothian Buses website has the details. Probably a better bet for getting you back to the station after than the shuttle bus too. Finish is at Pinkie Park in Musselburgh, opposite the racecourse, just off the main road.
OP - I am from Edinburgh and am running on Sunday too. There is plenty of on street parking just off the course. If you can get yourself to Milton Road East (A199) on your way into town on Sunday morning, you will get parked in the residential streets and can get the 44 bus to the start (towards town). It is pretty easy to navigate if you are coming up the A1. The route passes the end of Milton Rd at about 7.5 miles so your family can wait there or walk out or back along the route. There is a good viewing point at about 9.5 miles were we pass in both directions. There are cafes etc in Musselburgh if they need to kill a bit of time. You can then get a 44 bus back from Musselburgh to your car at the end. Simples.
I just switched from my normal Saucony Guide to Mizumo Wave Inspire as I found the Saucony's a bit stiff. It was a mistake. I find the Mizumo's too high round the collar meaning they run on my ankle bone when I am running on a camber. Did not notice this on the treadmill in the shop. They also don't seem to hold the back of my foot in place as well as other shoes. Have just bought another pair of Saucony in the sale.
I'm doing Aviemore 1/2. Can't find the elevation profile anywhere. I did the 10k last year and the start and finish points are the same for the half so I guess it is a net downhill. Any significant climbs on the 1/2m course? I'm not stressing too much about being beaten by Nessie having suffered the indignity of being overtaken by a giant oatcake in the Edinburgh 10 a few years ago, I'm over it.
I had/have exactly the same issue. I saw the physio for about 8 weeks last year - no real diagnosis but lots of massage and stretching which did not help greatly. I have since really ramped up my general stretching routine and made an attempt to get out of my office chair a bit more during the day as I am convinced the root cause is tight hip flexors. It's not 100% gone but these changes made much more difference than the physio.