How to easily build a cross platform app without much learning curb

I want to build my very first app and "post" it on the apple/google App store...

• I want it to be for both iOS and Android.
• I do not mind learning a new programming language.
• Cross platform, to write one code for both platforms. Can't spend too much time learning multiple languages :p
• I already know JavaScript/jQuery, MySQL, PHP, HTML, CSS, etc. but that's for web, not for apps...right? Wrong?
• I need to get it done fast, hence cross platform. One code, two OS (Android & iOS). I'll invest the time latter, in life, to learn each individual SDK. Not now.
• Stability: Since it's going to be cross platform, stability is important.

The App

It's going to be something similar to UPS, with pickup-delivery requests, etc. 3 apps, one for the client, one for the workers and one for administration.

Client side

• It needs to connect to a database
• Calculate distances based on the user address input (or current location/GPS) and the user input for the delivery address.
• Calculate rates, based on "driving distance" miles. Not linear distance.
• Provide delivery status (driver location), profferebly in real time if possible.
• Provide delivery confirmation

The worker side app

• It needs to receive the client's orders, based on what worker is closer to the client. Not all workers receive the same/all orders.
• It needs to feed the location of the worker back to the client, both before arrival and after delivery.
• Provide driving directions.
• It needs to have a way to save signatures after delivery.
• Provide a delivery confirmation to the client.
• Geolocation when delivered.

The administration can be a web or executable software.

Required

It may need more, but so far I identified these:

• Use the device's GPS
• Maybe it needs google maps API
• Authentication: Log in AND Device's MAC address, for both Client & Worker app
• MySQL database, to store all. Transactions,

Where do I start and what will I need?

You can use Html, Css, Javascript for building apps also. I will recommend to use phonegap which is framework used for building cross platform apps..you can get current location operation on database. etc here is link you can find more details about it from here.

http://phonegap.com/

there are other platform also you can just search cross platform apps on google.