It does sound a little ambitious to me...but you know your kids and yourselves best. Just remember that you are probably going to need to leave your house by 7:30 or so in the morning to get to the CP by 9 (and that is assuming your house is within 15-20min of the MK parking lot) since you have to park, catch the monorail or ferry, get thru the bag check and turnstiles and if it is a 9am rope drop day deal with that too!
Character meals are FUN but they don't lead to much actual eating for me or my kids...the kids are too busy looking around, dancing and playing with the characters, and watching what is happening at everyone elses table. I don't get to eat much because every time I want to go to the buffet another character comes and I would miss the photo opportunity! So I personally wouldn't do two in one day because no one really eats much...but that is me!
The BBB was really busy when we were there and the entire experience did take about 90 minutes...not counting the photoshoot. We didn't get in until 30-40 min after our appointed time. And my daughter kept messing up her nails! LOL! So plan on that and maybe you will get lucky and it won't be busy.
You can count on dinner taking at least an hour too...and the characters there were a hoot...they all stopped, really chatted with us, and were funny! So again, not much eating
I would personally plan a midday break in there and maybe split up the character meals into different days if you can. Eat breakfast at the house, go to the park for a while, come home, swim/rest give the baby a good nap and some time out of the stroller, then go to BBB, and dinner.
But this is all coming from someone who just did 3 waaayyy tooo busy days at
Disneyland and 3 character meals in 3 days and is a bit on overload...