Sometimes it can be difficult not to get attached to gear, first DSLR, bought for you by someone special, these are what keep me from disposing of my 300D purely for sentimental value.
Also as you state, a camera of low (er) value to take to the beach or to have available to capture that dust devil when I for one would not even think about using a new camera just in case. The T4i did not suddenly get worse, you will keep the pics from before you upgraded, so why not use it for keepers in high risk, dirty, wet or whatever the hazard is.
Or a bit of fun, I too have done some family weddings and once I had two bodies I would either set one on a tripod, or better a shelf where it can be made to look almost abandoned then trigger with a remote, I have a picture of a family member looking like a deer caught in headlights from this method, (the flash fired). Or a friends wedding I just put the camera on the tripod and made a time lapse film of the general reception area, whilst I wandered with the other body, that went down well.
Sell and buy what you need. Don't be sentimental towards equipment.