have heard men have to wear jacket and tie for dinner is this true?

Not true, you just have to be smart, ie long trousers, no shorts at evening dinner.
Straight opposite the Paradise Park are a couple of excursion and car hire shops - they will give you info about all trips and you can buy your tickets there.
For you with a young son I would say the 3 best days out are the whale and dolphin trips from LC harbour, a day at Jungle Park just outside LC and a day at Siam Park, Las Americas. (The last two both have free bus included) All these have reasonable journey times.
Can't emphasise enough how good Siam Park is by the way, its brilliant.
There are island tours but they are quite a long day and would think your boy may get a little bored? For visits to other islands, you can get the ferry to La Gomera from LC but once you get over there you still really need to go around the island on a coach trip so another long day.
Loro Parque in the North is excellent but again a very long day with early start.
Sure you will love it.