Ian,
Sorry, that will not work...The moment you switch on the 2nd TX with the same crystal fitted the RX front end will be unable to discriminate between the two FM carrier signals and will be totally swamped. The whole thing will then become very unstable and you will get no usable output from the TX, just random outputs or, if you are using dual conversion, more than likely no output at all as the RX may reject both carriers as it could see them as interference.