A&B .... my experience was totally different!
When we cruised DREAM last year, we booked two cabins .... one for our chidlren and their nanny and one for us. For the most part, it was a great experience. We did not have to do any "work' with respect to dressing, bathing etc. The children were always dressed and ready to go, and we had a built-in babysitter so we could enjoy the shows and the casino at night. Our kids were 2.5 and 4 at the time. It was a perfect experience except for the fact that our nanny (about half way throught he cruise) started to get facebook,texting,email, internet withdrawal and then turned into quite the grump. By the end of the trip, I could not even stand to be around her.
We figured what we would be paying in overtime for the week, would be offset by the cruise, and this way our kids got to enjoy it too. Plus we were expecting her to leave us last year (which we did) so wanted to take her on the cruise, hoping she might get some enjoyment out of it - which I don't think she did.
We'd do it again in a heartbeat except this time, we would have clearer discussions up front on expectations, work hours etc. We're taking the Eurodam in a March, and it will be just the four of us..... but our kids are older now and more self-sufficient (3.5 and 5). It still would be nice to have someone watch the kids though at night
To the OP .... I wouldn't personally take children under 2 on a cruise. You want them to be at least old enough to take part in the children's programs. Also, if they are not potty trained, they can't use the pools. My son was 2.5 when we cruised last year, but he is very advanced ... he was potty trained, very independent, was speaking in full sentences, conversational etc.
As for your son's blindess, I would not count on or expect any levels of service. You may want to call the cruiselines to discuss how they could help.
As for booking, yes watch for specials. We will not take our kids on Royal, because their 3rd/4th pax pricing is exorbitant for children. I should not have to pay the same price for my child that an adult would pay. IMHO, Carnival offers the best pricing for chidlren. We also just got a great deal on HAL, whereby we were paying $99 for the 3/4 passenger ....