Best things to do in Bournemouth for 3 day trip - also tips, voucher sites, dicounts, etc

[100KitKats]

Taking my 8yo son to Bournemouth for 3 days. Need advise about best things to cram in to get as many experiences in a poss including free/discount things or visual areas of natural beauty. Have been looking on www.bournemouth.co.uk but there is so much to choose from. On a modest budget but happy to extend budget for anything unmissable! So far the Oceanarium, Bournemouth Eye and the open top bus sound like ds kind of thing. Should we book the Eye in advance? Any recommendations for eating out generally (expecially Italian/Pizza/Indian) and restaurants overlooking the beaches for sunset/afternoon tea? If there is a previous thread - please let me know. Hope the weather is OK!

This is my favourite thing to do: Take a day trip to Swanage on the 150 bus (might not be open top, depends on the weather at this time of year). It crosses over the Sandbanks ferry, great views of Brownsea Island. Visit the steam railway (free access to the platform), then get fish & chips from Parade Fish Bar and sit on the quay to eat. If you get a rover ticket you can hop off at Shell Bay (by the ferry) and while away an hour on the beach watching the boats and hunting for shells.
Take a walk up Hengistbury Head and around Christchurch Harbour for great views and fresh air.

I'm going to cut and paste that into our list of things to do - sound like great fun. Leaving tomorrow and I haven't had a break in ages. Thanks.