1. Usually yes. Weather - last October first half was very good. Second, half, not so good. You can't predict.
2. Try Little Italy on the Pinewalk. Great pizzas at 6 or 7 euros. JKs Bar, Ctra Formentor, all sorts of well-priced very good food. Wherever you go, for 4 you'll usually be paying 50 euros minimum for what you want. No, it is no cheaper in Alcúdia.
3. The walk starts from the urbanisation of Siller. Over the by-pass road near to the Caprabo supermarket, opposite the old Tramuntana restaurant.
4. Bus to Alcúdia and S'Albufera. Same bus (line 352). Goes to Can Picafort. 6 or 7 kilometres to Alcúdia and double that to Albufera if you want to cycle. Safe? Pretty much, but there are a lot of nutters.
5. No scary big insects.
6. Best ice-cream is Ben n Jerrys on the main promenade. Bony in the church square for sundaes.

1) Will it be warm enough to go in the sea. What could weather be like.
October is usually very pleasant, although it can be mixed. Normal is shorts/t-shirts during the day, jacket or sweater in the evening.
Sea is usually quite pleasant for swimming.

2) Have a family of fussy vegetarians likes include pizza and pasta omlette and chips ect. How much would we pay for a meal for four with prehaps main meal, desert and bottle of wine. Is it cheaper to eat in Alcudia.
Lots of restaurants do a "Menu of the Day (Menu Del Dia)", which is a 3-course with drink for around 12 Euros per person. Personal favourite is TOTS in the pedestrian area behind the Chinese at the roundabout.

3) Where does the walk start from to Cala Sant Vincen
Walk is over rough hilly country, full details from the Tourist Info at the taxi rank.

4) How do we get to Alcudia old town and S'Albufera Wetland from Puerto Pollensa can we get a bus or how safe is it to cycle
Bus to C'An Picafort goes thru Alcudia and on to the wetland park. It's a long way along a very busy road.

5) Is there lots of scary big insects (daughters question)
No. Just mozzies.

6) Who does the best ice cream sundaes (Sons question)
The kiosk outside the 1900 Cafe by the main roundabout.

Thats very helpful many thanks for your detailed replies