Hi Lou
Returned from LG 3 weeks ago, we stayed in Limone. You will love LG it is so scenic! The ferry will take you most places on the lake, from Riva you can get the ferry to Torbola, Limone and Malcesine on the top end of the lake. Also you can get to Garda, Simone and Bardolino which is a longer trip and you need to catch ferry at approx 9 am.
We only managed to see the top half of the lake, apart from day trips to Venice, Verona and the Dolomites,
Riva is a very beautiful small town and sitting have a long leisurely lunch on one of the street cafes is pure decadance itself!!
Limone is very similary but definately worth the short trip.
Also Malcesine - you must go up the mountain in the cable car - the views are fantastic (on a clear day!!)
Would not hesitate to go back to LG.
I am sure you will have a lovely time -
Alison