Iphone 5 + iPad Air has much more valuable than one 5s at this stage in the game. The iPhone 5s is half way through it?s cycle and you are coming from a 5, and yes the 5s is faster (not always very obvious, I have compared them personally time and time again) and it has 64bit processor (not very applicable as yet, since few apps/features take advantage of it) so minus the fingerprint sensor, there is little difference. In my opinion it is certainly not worth it.
Calculations (approx)
iPhone 5 = 550 USD
iPad Air = 499
Total = 1049
iPhone 5s (32GB) = 749
Now since your devices arent new, you can?t sell them at original price, but if they are in good condition, depreciation can be as little as 50 bucks each. Your business plan would have you losing at least 200 USD. If that doesn't bother you, then go ahead. Or maybe you can wait a few months (till august lets say) sell, stick it out for a month or so, and get the brand new also 64bit but with possibly new bigger screen for the same price iPhone 6.