If you want to play anything relating to Silver Dragon working as expected, forget about anything less than paragon level campaign.
I would suggest making custom race and class, with fixed choices till 11th level, trying to emulate weakest version of dragon. Then, depending on time, either create single paragon class or few for choosing, all of them dragon specific. Also, create class powers till 30th level, with at least 2-3 choices on each level. I think that 'normal' epic destinies could be reused.
You will have to make sure that your at-wills are not too powerful - they will be probably in line with base attacks of weakest (3-4 lvl) dragons. For the rest of the powers, you can be more forgiving, but still try to keep things in balance.
Stat bonuses should be in sync with other races - but as you will start at 11th level, you can preallocate +5,+5,+1,+1,+1,+1 (or +3,+3,+3,+3,+1,+1) bonuses and pretend it all comes from dragon race. Same goes for feats - get few small powers/bonuses instead of feats you would get on lower levels.
HP should be allocated depending on the role. Silver dragon sounds like a leader probably, so set up hp accordingly (with possible +5/tier from feat). Being a dragon is no excuse to have more healing surges or hp than other players.
Breath weapon can be encounter power, without recharge possibility. Things like tail slap etc, which are at-will for monsters, should be probably encounter (or even daily) utility powers. Bloodied breath can be probably daily ability.
Generally, when balancing such characters, compare then to well optimized core PC of the same level. Your custom creation should be on average worse on many aspects, slightly (only slightly) better on one aspect. After all, you are doing it for RPG reasons, not to sneak in power-munchking overkill powers to overshadow your fellow players. Better to err on the weak side and beef it up on higher levels if really required.
