Keeping an unlocked 3GS and new iPhone 5 on same iTunes, what/how can apps be shared if not using iCloud?

Question

I have researched having two phones on the same account and keeping apps/music/contacts/etc.separate, but have not yet found a thread specific to NOT keeping everything separate but the same across phones; should be pretty simple, but simple sometimes isn't. Thanks in advance for your input!
My husband and I are electing to keep our 3GS' (unlocked) so when we travel internationally we can pop a sim in from the country we are in, mainly for data. (In one country we can get 500MB for 10 Euros versus the $25/100MB my carrier will charge with the iPhone 5.) At least that is what we hope...
Couple questions:
1. Once the cell number/service on the 3GS is transfered to the 5, the 3S will become basically an iPod touch until a new sim is in place, correct? We can still use wi-fi and the apps on the phone, and still be able to sync to iTunes, correct? iOS has been upgraded to 6.
1a. With a new Sim, any issue with losing any data/apps on the phone? I dont' think so.
2. Once the 5 is activated on the new carrier, how do I share the apps within iTunes? Is it as easy as using iCloud (which we haven't "activated" yet) and/or plugging both phones into iTunes and transferring between devices (authorizing both)? Photos? There are photos on the 3S that we will need on the 5.
3. Reverse order for new apps purchased (understand that not all the iphone 5 apps will work on the 3GS)?
4. My husband also has a new iPad, any complications there with three devices? To date, he has not "shared" apps between his 3S and the iPad. He does not have iCloud set up, but plugs into his computer to backup and transfer photos. 
Agian, thanks for your thoughts and any tips you can give me. Over the last three years with the 3GS, I have had to rebuild my phone twice and while most of the items were recovered, I am leery of throwing the 5 into the mix!

Answer 1

1. Once the cell number/service on the 3GS is transfered to the 5, the 3S will become basically an iPod touch until a new sim is in place, correct? We can still use wi-fi and the apps on the phone, and still be able to sync to iTunes, correct? iOS has been upgraded to 6.
1a. With a new Sim, any issue with losing any data/apps on the phone? I dont' think so.
1. Yes. without a sim it has no service, but all other features should be useable normally.
1.a Nope, Data and Apps are independent of the Sim.
2. Once the 5 is activated on the new carrier, how do I share the apps within iTunes? Is it as easy as using iCloud (which we haven't "activated" yet) and/or plugging both phones into iTunes and transferring between devices (authorizing both)? Photos? There are photos on the 3S that we will need on the 5.
2. As long as both Phones use the same Apple ID, the applications can be synced to each through iTunes. Also any downloads on one phone should appear in the other. Again as long as both phones are using the same Apple ID.
3. Reverse order for new apps purchased (understand that not all the iphone 5 apps will work on the 3GS)?
3. If they can be run on the iPhone3GS they should be synced automatically.
4. My husband also has a new iPad, any complications there with three devices? To date, he has not "shared" apps between his 3S and the iPad. He does not have iCloud set up, but plugs into his computer to backup and transfer photos. 
4. If all 3 Devices share the same Apple ID all should be synced. 
As a word of warning, if all 3 devices use the same Apple ID, messages recieved using iMessage will appear on all 3 devices.
And Conctacts may get overwritten if synced to iCloud (thogh you say he doesn't have one), or merged together.