Dear Ashikmurshed bhai,
You raised a very important issue. I don't think credit card could be used as an acceptable form for the first landing. According to the Forex Guidelines, you can take upto US$ 2000 as cash and the remaining amount ($3000) in TC. Most banks no longer trade in TCs after Amex left BD. But, I know for sure that StanChart does. So you can take US$ 10000.00 in cash or near cash form for you and Bhabi from StanChart. As for the child, the limit is half (US$ 1000 cash and US$ 1500 TC). That makes a total of US$ 12500. You don't have to be a client to avail the service from SCB. For the rest, I am afraid you have to carry cash without endorsement. Someone in the forum suggested that we take 1000 Euro note as that would be easy to hide. Personally I would carry Canadian Dollar as much as I can in order to avoid the exchange rate loss. I think you can devise your own strategy like keeping the unendorsed cash in small bundles in different parts of your carry-in luggages, wallet, purse and so on. Hope that helps!
PS.If you had an RFCD account, you could take the whole amount without any problem.