hair extensions, holiday and shampoo

[iwantextensions]

just new to the site and think i posted in the wrong place... having a bit of a hair issue.. i am going for a brazilian blowdry on tuseday and then having weave in extensions fitted on friday, i am unsure what shampoo i should use as i need to use sulphate free shampoo to make my blowdry last, but not sure how that will work on extensions (its remy grade 3 or 4 hair)

also am going on holiday on sunday so not sure how my hair is gona be in the sun?? any advice welcome! x