Dear Brother,
Unfortunately I differ from your suggestion. The reason is, if you see the conversations of this forum members then you will see everyone is concern about limitations of carrying foreign currency from Bangladesh. It is good idea to get EBL or any bank's Pre-paid card for this sort of transactions but unfortunately without passport endorsement you are NOT allowed to make any International payment by Bangladeshi cards. As there is obligation that principal applicant has to carry minimum amount of fund during first border crossing, so if you deduct your yearly travel quota now then you are deducting by own to buy/endorse full amount of allowed yearly travel quota Dollars later. The MOST IMPORTANT thing is that if you make DD from any bank in Bangladesh, This sort of Immigration fees are out of yearly travel quota limit, so that if you pay through DD then during final leaving Bangladesh, you can carry the whole amount of your yearly travel quota amount. However, I strongly recommend you all, if possible use your friends/relatives CC to pay to avoid hassles by SCB and long time consumption to en-cash DD.
Regards