My daughter is 10 months old as well and eats 3 meals a day, and is breastfed. Sometimes she has dry hard poops and I always make sure I watch her intake of rice, bananas, applesauce and cheese. (YES- applesauce is bad for constipation!!) You can try switching from rice cereal to barley, because it has more fiber and does not cause the constipation that rice does. This helped my daughter a LOT. My ped told M. to give her peaches, pears, plums, apricots, peas, and green beans. The ped also recommended a little bit of apple or white grape juice. (But not applesauce!) The sugar in the juice helps get things moving.
I introduced a sippy cup of water with my daughter and she has that during her meal times. Babies typically don't "need" to drink water, because the breastmilk should provide plenty of liquid, but learning how to drink from a cup will a very important skill in a few months.
Just a side note, the reason that we aren't supposed to give our babies milk before the age of 1 is not necessarily due to allergies- it is because cow's milk has empty calories and no nutritional benefit for children less than 1. So you shouldn't have to worry if there is some dairy in your son's food. In fact, yogurt with active cultures is SO GOOD for babies over 8 months- (providing your child doesn't have sensitivities to milk.) The active cultures definitely help with constipation problems because it puts good bacteria into the colon.YoBaby and Brown Cow (cream top) are 2 whole-milk yogurts that have live active cultures. Lots of sugar, yes, but unless you make your own yogurt, get used to the sugar thing... :)
A great website that has recommended ages for solid foods is wholesomebabyfood.com. Even if you don't plan on making your own food, this website has almost all the information you could ever need!