Hi,
I've soldered for a good few years and found smd a pain to get used to, although with practice you do get better.
As for someone buying one of your kits, I would have to assume the majority will be beginners to soldering and smd seems a step too far, I would say.
You are then expecting them to buy extras like a suitable tip for the iron and a flux pen etc.
I'm sure standard parts would be a challenge for quiet a few of your users never mind trying to deal with smd sizes.
I would have thought for your kits it would be possible to have the smd parts pre soldered or at least the option when buying to request that they are pre soldered .
hth