Organise truck space

I work in a freight company that operates in Europe and is stationed in Croatia, and we have 8 trucks with cooling and we mostly drive cut flowers so that means that going from point A to point B needs to happen fast. We also mostly drive for more clients in one go so that means that our drivers have to collect pallets from a few places(all from different clients) and then they drive to (for example Croatia) and then unload it all. Now what happens is that drivers sometimes don't load the pallets that well(you have to have in mind that sometimes they have to unload pallets in a specific order and if drivers mess up in loading the truck, they have to unload all the pallets that are in front of those that they need, and that means that we lose time and time is key factor). So what we need is an app that will allow our boss to organize a truck with drag 'n drop style interface(will add sketches) which will have all the information that will drivers need(Name of the client, address, time of load and unload). The squares will resemble the length and width of pallets(There can be only around 10 possible lengths and widths for pallets and trolleys that will be in the system). Boss will choose which type of pallet it is(size), then he will add the info to it and then he will drag 'n drop it into the ground plan of the truck(we could make different colors for each square, depending on the client). Now that is the function of the boss, but drivers will only get to see finished ground plan. So there will need to be a log in to know who is the driver and who is the boss. There will also need to be a feature that will allow us to add more trucks and to enter trucks size, they will be different by number plates and the boss can see all of them while driver can see only the one that he is assigned to(boss will also assign drivers to their trucks). If it would be possible to make this an Android app and an desktop program that would be all connected. These are the plans for future, and of course we would prefer someone that would make all of this together and not one person for iPhone and other for Android.