We have recently returned from the Seychelles as part of our honeymoon and it was so beautiful! We stayed on Praslin island at the Raffles resort- which was gorgeous but....expensive! The service and rooms couldn't have been better, the food was also very good. There were a few under 5's there. Praslin is the second largest island. Mahe (the largest) is quite a big bigger and busier than Praslin. You do have to take a very small plane for 15 minutes to reach Praslin from Mahe. If you get the chance make sure you visit La Dique whilst you are out there- it's an island where there are very few cars and so basically you cycle around all day between the beautiful beaches and you can see the giant tortoises too.
Also be aware that if you have any leftover local currency (Seychelles Rupees) then it's very hard/impossible to find somewhere in the UK who will exchange them back into sterling. We weren't aware of this and so we have 1060 Rupees (£50) leftover. Please let me know if you'd be interested in purchasing them from us for your trip.