Have just recently been to Taba. the visa is done at the airport. When you come through customs they will ask you whether you want just Sinaii only or whether you intend to go to main egypt such as Cairo. ( it is quicker to get the sinaii only).
You can take a visa if you want to.
The egyptians take most forms of money. When we were there just before xmas, £1 was worth 11 egyptian £'s. A euro was worth 7 egyptian £'s. Don't know about dollars. Most hotels have a cash machine and also a bureau de change. Drinks can be pricey in the hotels so i would buy from the supermarket at Downtown where we got 6 litre bottles of water for the equivalent of 90p. Best if you buy your booze at the airport in England as it is very pricey in Taba ( £3.50 for half a lager, £4 for a shot of voddy, £4.60 for a glass of wine etc)
i didn't do the trip to Petra but i did to the trip to jerusalem and that included eilat. It would be a long day for your daughter if she is only 6. There is a lot of walking involved and getting across the border is very time consuming and frustrating. (took us 2 hours). Eilat is very Americanised and very touristy. I would probably recommend the trip more if your daughter was older..but i am basing that answer on what my kids were like at that age..you know your daughter's capabilities and tolerance levels better than we do.. the trip to Jerusalem was well worthwhile but it is an adult thing. There are trips to Dahab etc available too. I think your daughter would like to go on a camel..and the snorkelling is just out of this world....we stayed at Hyatt regency but the other hotels looked pretty good too, we visited them all!
Enjoy your holiday..