Couple of points:
1. There could be a few more announcements of new shows previewing by November. Might want to wait, particularly since you will be able to get discounted tickets for GHD -- which everyone seems to be recommending -- unless it closes before then (which I am expecting).
2. Consider Donna Murphy for Hello Dolly. She is a 5 time nominated, 2 time Tony winner. You will LOVE the show, and save a lot of money in the process. I saw Bette in HD and loved her in it; but, IMO, she couldn't hold a candle to Carol Channing or Pearl Bailey. I haven't seem Murphy yet in Dolly (she hasn't exactly been in a lot of performances yet and I am out of town), but hope to see her in October; and, despite the 'loss of event' associated with not seeing Midler, it is still a wonderful show and she is a wonderful musical performer.
3. Don't count on Miss Saigon being open IMO. Come late August, it is going to die.
4. Re Beautiful, I don't know where you live, but it has been touring the country for several years. Might want to see if it will be anywhere near you...why waste the 'slot' if you don't have to.
5. Come From Away is a very enjoyable, feel good show. You can't go wrong...just don't expect too much.