Travel expenses reimbursement

For exchange rate, you are doing right thing

book the expense a clubbed/aggregate including flight exp., visa fee, forex (in INR) that might you have paid to your employee before leaving INDIA, expenses that you have mentioned above

Try to present it in a excel sheet as a supporting voucher + bills if any whether in INR or AED including print out/sheet how exchange rate is taken/considered

Whatever employee has spend from his own pocket get the details in proper format or in plain paper signed by employee, then you can pay him through cash or  bank(advisable)