UK Holidays in the SE

Wondering if anyone has good suggestion for 4 or 5 day holiday in the SE?

Here's our info:
*My wife will be 8 months pregnant at the time (June) so a relaxing holiday not active!
*We have a boy 30 months of age
*We live in Greenwich (London) and prefer not to drive more than 3 hours
*Perhaps spa/message treatment for my wife as an extra treat?

We've already done Brighton, if we do another beach we'd like sand not rock

I saw Bournemouth on-line, anyone been there?

For something close by my DW suggests Rowhill Grange near Dartford.

http://www.alexanderhotels.co.uk/rowhill_grange/

We have been to the beach at Bournemouth for just a day.  I can vouch for the nice sandy beaches and convenient parking.  It would be a good beach for your son.  I don't know what else there is to do around there so I'm not sure if it would be a good 4-5 day trip.  There was a pretty high hill that many people were walking down (from hotels, I suppose) which might be uncomfortable for your wife.

What about Isle of Wight?  I haven't been there but it seems like there is lots to do.

Not SE, but SW, when I was 8 months pregnant we went to south Wales for a short break. we stayed in Mumbles which is on the coast, a lovely little village, very family friendly area.

Otherwise I would perhaps recommend Folkestone in Kent. Again, on the sea. The beaches are mostly pebbley but there is one sandy one and there are various play parks for children in the sea front area too. Broadstairs is another nice seaside town in Kent, with a big sandy beach and again very family friendly, we had some lovely days out there when we lived in the area. 

Thanks for the suggestions, I'm going to check it all out tonight and hopefully get something booked.  Time is running out before our lives are turned upside down again!