I say go for CRT - Every princess should eat in 'the' castle once and they are a perfect age!
Went when my daughter was 6 for first visit. we did Akershus, it was great, but now that she is 13 and we have never been to CRT, I wish I splurged for the two credits just for the magic of going in Cinderella's castle
I think it is booking for dinners in March so I assume you may get a reservation in April.