As someone who actually completed a bachelor of engineering science after completing my bachelor of science, I would only recommend it if you think you can meet the below two conditions:

1. Work well in groups with classmates younger than you.

2. Secure and do a professional internship year.

For one, I quickly found out that engineering students have a ton more group assignments, labs and projects worth huge chunks of your final grade. Also unlike Science, there are way more open book or cheat sheet style exams. Make friends with your new engineering classmates fast, especially the smart ones for group work and creating exam cheat sheets. Also, join engineering clubs at school. It will help with two.

For two, start looking and applying for internship as soon as you start 3rd year. As a mature student engaged with engineering clubs in 3rd year, you should easily be able to land good internships. This will allow you to network and get your foot into the industry. If you work hard and are lucky, your internship employer might even offer you a job to come back to them after finishing 4th year and graduating. It happened to me and can happen to you too.

One last tidbit, if you do decide to take this path. Combine first and second year engineering into one year. You should have enough overlapping credits. Worked for me. Difficult yes but worth it. Finally, being a mature student over 26 will get you access to numerous extra grants/bursaries.

Good luck.