Just an opinion. I wouldn't worry about trying to find a reseller that also provides a domain reseller account. If you find one, that's great, but make sure that you and your clients will have a 'real' domain registration control panel. By 'real', I mean an actual registrar control panel versus a reseller's API.

You might also consider having the domain reseller account with a different company. The old adage; 'Don't keep all of your eggs in one basket" applies here. If you have a problem with your hosting reseller, say late payments, whether it's you missing a payment or the hosting reseller's accounting error, you may not only be suspended from hosting reselling, but also domain reselling and their respective control panels.

I'm not making any accusations against the company you've chosen, or any other specific company. However, if you read through these forums, you'll see horror stories. I'm sure there are some that are a work of fiction, but there's some that are without a doubt true.