You could try one of these ways.

If your restaurants are in A1:A20 then put this formula in B1 and copy down to B20

=rand()

Then sort columns A and B, using column B as the key....and use the top 5 restaurants.

If you don't want to alter the restaurant list then use the rand formula as before then in D1 use this formula copied down to D5 to give your 5 restaurants

=INDEX(A$1:A$20,RANK(B1,B$1:B$20))

Note: you can hide column B if you wish. 5 restaurants will be re-selected if worksheet re-calculates (hit F9 to to this manually)