The bus that goes from Varna rail station directly to Golden Sands are 9 and 109.Those buses do not enter in the inside of the resort complex - they go only to its entry.You can use them from the first to the last station and then enter the resort walking - you will certainly find your hotel - it is on the beach alley
Buses pass on interval of 30 minutes together (60 minutes each line) and stop on the bus stop not just in front of the station but the one on the opposite side of the street. If you want a bus going inside the resort you must take bus 409 express (you can distinguish from normal 409 by the colour of the number which is red).Unfortunately this bus doesn't go to the station and you must take other bus to make correspondance (I can not help you with the number of the line that you take because I'm not from Varna I also went to Golden Sands in June and had to discover all of this by myself).Anyway 9 and 109 are better option I think.
Tickets cost 3 BGN (1.5€) а person but if you bring big cases you will be asked to pay 1 BGN for each one (0.5 €).Tickets are sold by a woman in the bus.If you are more people it's better to take taxi from the station that will pick you up in front of the hotel it will cost you approximatively 20 BGN (10 €).As far as I know there is no possibility to take one day ticket for all the lines in anyone of the cities you mentioned:(
Trolley line 88 is still in service in Varna as 82 and 83
Wish you a nice trip and sunny weather,water's temperature now is 30-31 degrees