I'm afraid that there are no provisions that make business asset rollover relief available to rollover gains made on the disposal of non EEA property let as holiday homes into the purchase of another holiday property, albeit in the EEA. The property has to to be let in the UK or the EEA and comply with the furnished holiday let rules to be able to access business asset rollover relief. Even if the properties were owned by a company and you sold your shares (the business asset in such a case) you would probably not be able to claim as the business is primarily that of letting property which successive UK governments have always seen as an investment business as opposed to a trading business. It does seem unfair especially if you have been heavily involved in the running of the lets.
You may be interested to read about a tax case on rollover relief on let property here.
I hope this clarifies things for you but let me know if you have any further questions.
I have to go out for a while but will back in 30 to 40 minutes to answer any follow up questions you may have.
The gain will need to be disclosed in the UK using the relevant rate of exchange (US$ to UK£), regardless of the US$ being converted directly to Euros to fund the property purchase in Europe.