Emmalou, do make an effort to take your children to Tango. They will be welcomed and looked after. There's also plenty of choice on the menu for the girls.
We always feel safe walking in P.P., day or night. It will still be light in early evening in August, so no problems on that count. The suggestions above are all good. The bus is very cheap if you choose that, it's also a beautiful walk. Our preference was to get a taxi to Tango from the Marina Taxi Rank and walk back with no bother about how long it took - about 25 mins if I remember correctly. Though the choice is yours. As mentioned above, the staff at Tango are more than pleased to ring a taxi for you if you don't want to walk back, and it shouldn't break the bank. You could enquire about taxi fares earlier, before you set off.