I'm working on a city but I think I may be making it too big, but I'm not sure and am looking for some advice

Currently it is 10 miles x 7.5 miles. SO the basic question is how big should I make this city

A little about the city and the campaign it will be used for

Basic Geography
Center City lies between two mountain ranges which cuts the Northwest part of the continent off from the rest of the continent. The two mountain ranges at this point are about 150 miles a part from each other and each house a different Dwarf Clan. It is on a major river and has docks for ships going up and down the river. It is a temperate climate region (think the climate around New York City) with 4 seasons. Temperatures rarely go below 0 or above 100 degrees

The racial demographics are approximately as follows
85% Human and Halfling
5% Dwarf
<10% other races
<1% Elf

Total population is greater then 25,000

Basic History
The city was once a simple fishing village under the protection of a noble family. There was a civil war in the ancient Kingdom, and this noble stayed neutral. Because of that he was forced to flee to this town. The ancient kingdom completely collapsed itself so no one came looking for the noble or his family.

The village grew to the size of a small town, but wasn't constantly attacked by Barbarians, Orcs, Gblins etc so couldn't grow beyond that size because of the attacks.

A war broke out between the two clans of Dwarfs, and the nobles (Descendants of the noble) brokered a peace between the two clans and as a part of the peace plan, so the two clans could get used to working together built a keep for the town.

Because of the keep, ad with help of the Dwarf clans the attacked basically stopped and the town started to grow.

About 150 years ago the noble family was overthrown by the wealthy of the city and it now ruled by a council which one member from each family who has a total net worth of 500K or more (less then 1% of the population) plus elected representatives (voted on by land owners) from throughout the city the total of which is two less then the amount of people who are on the council because of their money. (Yes the government is now mainly run by plutocrats, which means a lot of corruption.

Some City Features
The city wall was completed 100 years ago and is pretty well maintained because most of the land outside the city is still wild land. Before that it was unwalled except for the keep itself.

The keep itself is approximately 800'x800', 3-4 stories high (plus a basement level (maybe 2)). Entrances through the wall of the keep are only on the east and west sides of the wall.

A Coliseum
A Great Library
Dwarf District (nicknamed Dwarf Town) to the south of the keep and a Noble district (all the people with that high net worth) to the north

Campaign
There were 4 (Maybe more) Thieves guilds (think more like present day Organized crimes. They dealt with the tradition pickpockets, extortion, protection, assassinations etc.) However there was a meeting for the leaders of the four guilds and the city guard came in and arrested the leadership of all the guilds (executed the morning publicly). The headquarters of all the guilds were hit by the city guard that night as well as many of the various safe houses of the guilds. The total upper echelon of the guilds were either arrested or killed and will most likely be put to death soon.

The campaign will start the morning after where the players, who were part of one the guilds, went to an inn which was one of the neutral territories for the guilds.

I have no ideas what my players are going to do, Though there is a story of things going on, what role they play I don't know because I have decided to leave this campaign open from the player point of view. They may decide to be one of the ambitious people and create a new thieves guild, or decide to try and find out how the guilds were taken out so easily, or decide to go the traditional adventurer (I hope not the traditional adventurer) route.

So how big should i make this city?