Tataniano made a highly promising debut over fences at Exeter last week, winning a beginners' chase by 32 lengths. Paddy Power make him their 8-1 co-favourite for the Arkle next March.
Stewart said: "We have to find out how good he is, although Crack Away Jack will win the Arkle in my opinion!"
Lavelle isn't about to shirk the challenge. She added: "The problem with the lack of rain is that there are a lot of trainers waiting to run their horses and so all these races will be ridiculously contested. But Sandown is the plan."