I remember thinking that dd wasn't getting enough calcium...until I looked it up and saw that she was having plenty! Aim for 500 mg as an average. 8 oz of milk has 300mg, so you'd be more than halfway there with a serving of milk, even if he sips it throughout the day. My dd didn't love milk, but we got it in in other ways too...like adding it to oatmeal and adding it to french toast/eggy bread mixture. You may find that if you really track it, it isn't as bad as you think.

Here is something I found for you:
How much calcium does your child need?
Ages 1 to 3 years: 500 milligrams (mg) per day
Ages 4 to 8 years: 800 mg per day
Your child doesn't have to get the recommended daily amount of calcium every day. Instead, aim for that amount as an average over the course of a few days or a week.
The best sources of calcium
Dairy products such as milk, yogurt, and cheese are some of the best sources of calcium, but you'll also find it in less expected places. Some calcium-rich foods to try:
•1/4 cup raw tofu, prepared with calcium sulfate: 217 mg
(The calcium content of tofu varies, depending on how it's processed. Check the label.)
•1/2 cup low-fat plain yogurt: 207 mg
•1 tablespoon blackstrap molasses: 200 mg
•1/2 cup low-fat fruit yogurt: 122 to 192 mg
•1/2 cup calcium-fortified orange juice: 133 to 250 mg
•1/4 cup part-skim ricotta cheese: 167 mg
•1/2 cup milk: 150 mg
•1/2 cup chocolate milk: 144 mg
•1/2 ounce Swiss cheese: 112 mg
•1/2 cup vanilla frozen yogurt, soft serve: 102 mg
•1/2 ounce cheddar cheese: 102 mg
•1 slice calcium-fortified bread: 100 mg
•1/2 ounce mozzarella: 91 mg
•1/2 slice cheese pizza (fast food chain): 91 mg
•1/4 cup collard greens: 89 mg
•1/4 cup homemade pudding (from mix or scratch): 76 mg
•1 tablespoon tahini (sesame seed butter): 64 mg
•1/4 cup turnip greens: 62 mg
•1 ounce canned pink salmon, solids with bone: 61 mg
•1/4 cup cooked spinach: 60 mg
•1/2 cup ready-to-eat cereal, calcium fortified: 51 mg
•1/2 cup soy beverage, calcium fortified: 40 to 250 mg
The amount of calcium a food contains will vary somewhat, depending on the brand, the size of the fruit or vegetable, and so on.
Kids may eat more or less than the amounts of food shown, depending on their age and appetite. You can estimate the nutrient content accordingly.
Tips for maximizing your child's calcium intake
Some experts believe that many children are falling short of their calcium requirement, in part because juice and other nondairy drinks are so popular that kids are drinking less milk. Here are some simple steps you can take to make sure your child gets enough calcium:
•Use milk instead of water when making cereals, hot cocoa, and soups.
•Use evaporated milk in place of regular milk in recipes – it has twice the calcium of regular milk.
•Add yogurt to fruit salads; nonfat milk powder to pancake batter, sauces, and smoothies; and cheese to vegetables, sauces, and mashed potatoes.
•Buy calcium-fortified juice, bread, and cereal.
•Vitamin D helps the body absorb calcium, so make sure your child is getting enough vitamin D, too.
Also....look at this list...it isn't too hard to hit the mark when you add some of this up over the course of a day!
Food Amount of Calcium in milligrams (mg)
1 Tbsp sesame seeds 90
1 Tbsp Tahini 63
1/4 cup Brazil nuts or hazelnuts 55
8 medium sardines (canned) 370
3 oz salmon 180
1/2 cup oysters (canned) 60
1/2 cup shrimp (canned) 40
1/2 cup bok choy 75
1 cup kale 94
1 cup broccoli 178
1 cup celery 54
1 cup cooked green beans 58
1 cup cooked butternut squash 84
1 cup cooked sweet potato 70
1 medium naval orange 56
2/3 cup raisins 53
10 medium dried figs 269
1 cup calcium-fortified orange juice 300
1 cup enriched soy milk 300
1 cup enriched rice milk 300