Excellent choice going to Myanmar. I'm glad you'd decided on it so I didn't have to come in here and tell you the many reasons why you should change your mind!
I was there in May last year and what you're planning sounds like what I'd do if (more like when) I go back. I didn't get to Mandalay because the heat was simply unbearable in May (all of the 6 days I spent in Bagan hit 47C) so I spent extra time exploring Bagan at a very leisurely pace. Bagan was definitely a highlight, such a quiet pace of life and the most wonderful people I've met anywhere. Discussing the finer points of football while watching the FA cup final late one night with the hotel staff in their little bungalow is something I'll never forget. Good choice on missing out Inle Lake too. I ended up leaving there sooner than I thought and spending extra time in Yangon instead. It's really a bit of a tourist trap (by comparison to the rest of the country) and the people just didn't seem anywhere near as happy and friendly.
If you want to know anything else just let me know, but guesthouse staff there are just wonderful and will sort out flight/bus/train tickets for you without batting an eyelid and are more than willing to give you advice on anything once you get there.