We have done every character meal at WDW (and Disneyland). I kind of have a little addiction to them. I say it's all for my son, but really it's my addiction
There are reviews of most of them in my TR below.
I would say Ohana breakfast is the best. The food is really good, it's not a buffet so you can sit and relax at the table and have the food brought to you. It's served family style. So it's a set menu but it's all you can eat, so if you run out of something you can just order more. The food is placed in the middle of your table and you help yourself. I have pictures in my TR below

The characters are fabulous too!
Chef Mickeys really is our least favourite. The food is really very average and the character interaction is very rushed.
Crystal Palace isn't bad but to be honest, if he is a mature 5 year old, he may be a bit over the Pooh characters

If he likes pooh characters then that may be a good meal.
Tusker House is good. The breakfast is yummy, buffet and the character interaction was good. Having Donald, Mickey, Goofy etc in all of their safari gear, makes it a little more boyish. The setting is also rugged so would appeal to a boy of 5.
Garden Grill. Dinner, also served family style. It's not a favourite, bit it's ok. The food is really not good, we are not huge fans of it. Character interaction was great on most visits. Chip and Dale are there and they are funny and really played up to my son, so that might be ok.
Cape May's breakfast is good, the food is delicious and the character interaction has always been good. They used to have chip and dale there but they have moved on now and although we ate there three times last trip, it still was not as fun as when they were there. But it is still up there as one of our favourites.
1900 Park Fare.... Well this could be fun for your DS. Breakfast has the mad hatter and he is a scream! On our trip before last we had probably the most character interaction/fun of any character meal we've had, Mad Hatter was being so loud and when he came to our table my DS took off up to the buffet. He was hiding waiting for Mad Hatter to go past. Mad Hatter asked where my DS was and I said (silly me, LOL) that he was up at the buffet... hiding... he was scared of you. OMG! Was that a mistake! He was bellowing "scared of me... scared of me.... where is he.... what's his name" and then he started off around the restaurant screaming his name, looking for him, it was SO funny! My DS eventually came to the table and Mad Hatter sat down beside him and had a big chat. It was so much fun! They are just so funny and over the top but we went with friends who had daughters, we had not been before with just us and no other girls, so your DS may not be so into the princesses, even though there is a prince.
If you eat at Chefs de France and get the right time, you can see Remy. He comes around the tables on a trolley with a chef. He as a classic. I'm not sure if I have added the photos yet in my TR but if you want to see them let me know and I'll post them for you.
So our preference, with a boy is
1. Ohana breakfast
2. Tusker House
3. Cape May
My son's favourite restaurant is Sci-Fi dine in theatre. He absolutely LOVES sitting in the cars, thinks it's so cool.