I am further down and about as West as you can go, in St Davids. The Ribbing around here is excellent and very varied.
The coastline is spectacular and with a good day and a decent boat you could access anything from Strumble Head to Milford Haven or any one of the numerous offshore Islands.
The only thing that might be a problem could be the weather, what might be exciting for you might be a bit much for a family! And as might have been mentioned before there isn't much shelter out here
As per launching in St Davids there is Porthclais harbour (small launching fee), it has a slipway at high tide and a bumpy harbour floor at low. It its possible to launch at low tide but would would need a 4wd. Porthclais also have holiday moorings, but I am not sure of the cost.
South of St Davids is Solva (small launching fee), a much more sheltered harbour that i think you can launch from from anything above mid tide and North of St Davids is Porthgain (small launching fee) that I think you could probably launch from at all tides, further north again and you have Goodwick, Fishguard and Newport that has been mentioned before.
On the plus side there are lots of family friendly beaches around here and even more if you have rib
Staying around here isn't that cheap though, the campsites are at least around £10 per person in August and Holiday cottages start around £600 i guess? I have seen quite a few people with ribs camping at Porthclais campsite,
Here is a link to a "local" website of places to stay and info