I like the order of progression. We did something similar on our one MK day in August. I FPP 7D around noon, Splash (which was is not a roller coaster, but was making mine nervous, too) around 1, and Space around 5 PM (BTMR was closed for our trip). We rode the Barnstormer standby several times in the morning. DS8 didn’t love Space, but he did it, and I don’t think he would have if he didn’t have those others under his belt.
2 days later he rode RnR and loved it!
At AK, I recommend a few rides on Primeval Whirl before venturing to Everest (even if it means longer lines).
I had to laugh about the hair. When DS was 6, he was almost 48 in, and we didn’t cut his hair for months in anticipation of a trip to Busch Gardens!