Haha. Great! I'm in Bangkok now , but really missing Laos. Its not so big city but still a lot of things to do there. You can visit Mekong River for relaxation , exercise , mingle with locals. Lao people are very nice and many of them can speak English. You can visit local market beside of the river.
And some historical places in the morning like Lao national museum , Patuxay Monument, Buddha Park.
For nightlife there are some bars and clubs , go for HomeClub it's nice one, and open till late night 4am.
If you have time you can take a bus and go to Vang Vieng, 2 to 3 hours from Vientiane. Nice place for visit and travel , full of foreigners mostly.
Welcome! You can change both Baht or dollars to Lao Kip. I just got back from Vientiane on Sunday , and got the exchange rate 248 Lao Kip for 1 baht. You can change at airport or inside the city.
Baht is acceptable anywhere in Vientiane. But some shops or vendors may charge you higher conversion rate . Better to convert in Lao Kip there . Good luck :)