Multiple update statements in one StoredProcedure

Yes, that works fine.

Also put this in the stored procedure before the updates:

set nocount on

This keeps the stored procedures from creating result sets for queries without a result. Otherwise each update will produce an empty result set that is sent back to the client.

Yes, it's possible:

CREATE PROCEDURE prc_update (@table1_id INT, @table2_id INT, @table3_id INT, @new_value INT)
AS
BEGIN
        UPDATE  Table1
        SET     field1 = @new_value
        WHERE   id = @table1_id

        UPDATE  Table2
        SET     field2 = @new_value
        WHERE   id = @table2_id

        UPDATE  Table3
        SET     field3 = @new_value
        WHERE   id = @table3_id
END