Can someone help me with some good reasonably priced restaurants in Manhattan that would be appropiate for children?

Tennessee Mountain House in Soho; excellent ribs, good looking burgers (I keep eatingthe ribs, so can't say for sure) and fairly reasonable prices. I've been there with a 12 year old, who enjoyed it.
If America is still in business (on some east-west street in the 30's) kids will enjoy it. When I was last there, there was a magician on Sundays.
The atmosphere in the Carnegie Deli is almost as good as the food, and it has a special New York feel to it, too.
Hard as it may be to beliueve, the cafeteria in the basement of Trump Tower on Fifth Avenue has reasonable prices and good pizza and strikes a balance between casual and elegant, and bigger kids may be impressed. Most of the restaurants at South Street Seaport are kid-friendly and reasonable, too.
BAK
BAK

Further to the above; America appears to still be in business, but I got the address fairly wrong; it's 9 East 18th Street, between Briadway and 5th Avenue.
BAK

There's amore convenient Tennessee Mountain on West 45th Street, between Broadway and 6th Avenue. In a similar vein in Virgil's BBQ on West 44th between Broadway and 6th Avenue. The food at both is decent and reasonably priced. You should have no trouble getting in either without reservations.

I tried to post this earlier but it didn't go through -- hope this time it works.

Serendipity 3 on 60th b/t 2nd & 3rd Aves is a great ice cream parlor, basically a must-do if you have kids. Frozen hot chocolate, the best sundaes ever, and a "general store" with stuff to buy.

Chat 'n' Chew -- I think it's on 16th, between 5th Ave and Union Square. Lotsa comfort food (mac 'n' cheese, burgers, fries, giant layer cakes) in a casual, white-trash-hipster setting.

For pizza, John's and Two Boots are both good for families (TB is particularly kid-friendly) and they have good pizza, but if you want the best pizza it's got to be Lombardi's on Spring St. (John's and Two Boots both have multiple locations.)

For breakfast, you should definitely go to the Pink Tea Cup. It's in the West Village and has some of the best pancakes ever! But, go early because it's a small restaurant and the wait can be a bit long.