If I was you, I wouldn't buy them from the travel agents. You might not want to go 2 days and I think that they have to be 2 consecutive days too.
But it's entirely up to you, if you think that you would visit twice then it's probably a good deal.

We went late afternoon which is at a special rate. We had adequate time to get around at about half the normal price which was a good saving for 4 of us.

Sue

Thanks Sue for that bit of information i will talk it over with my friend as we are going together with our kids

Sharon

We went last year armed with our credit card to buy 3 two day tickets, however they would only accept this with our passport for further ID. Guess what we did'nt take with us, our passport so we had to scrimp all our money together (including the bairns spending money ) for the entrance fee, which we could only manage 1 day, and our lunch. This put a dampener on our day. We were glad we only managed to pay for 1 day as we wern't impressed.
The park was okay but Tom could'nt go on much due to height restrictions (he was six at the time). If you've been to Port Aventura in Salou, you are in for a big let down here. I would sayTMittica is more geared for bigger kids although there is a small kids section tucked away at the back of the park.
I'd recommend getting a taxi there and back as the buses get chocabloc and they seem to let as many on as possible, not very safe in my eyes. Its about 10 euros each way.
If you go, prepare to spend a lot of time walking as everything is spread out.

we booked our tickets for terra mittica last year through our travel agents. The buy one day get one free thing is over two consecutive days, which we thought was a bit stupid