Yup, no worries at all. Your pets are and will be completely safe.
Progress is related to Pixpet Adventure which can be seen as a side game/extended feature. Entirely different system from the current web version with hoards and what not. The only thing the beta testers will have reset is their adventure levels so that everyone will be on the same playing field when we hit launch as items and such can be transferred between the game and the main site. Wouldn't be fair to all for them to be far ahead.